First Look At The First Flower, Ancestral To All Others

Posted, but mnot written by, Lou Sheehan

First Look At The First Flower, Ancestral To All Others

By Gemma Tarlach | August 1, 2017 10:00 am

The first flower, revealed today by researchers in Nature Communications, is more than 140 million years old. (Credit Hervé Sauquet and Jürg Schönenberger)

About 90 percent of all terrestrial plants today are angiosperms, or flowering plants. Yet finding the flower ancestral to them all has been a, ahem, fruitless search. Until now.

Although plants do turn up in the fossil record — such as the stunning 52-million-year-old tomatillos revealed earlier this year — some of the most important, evolutionarily speaking, remain elusive.

Such is the case with the first angiosperm, which researchers estimate evolved between 140 million and 250 million years ago. Once on the scene, flowering plants diversified rapidly, spreading around the globe and taking over from the previously dominant gymnosperms (which today survive as conifers, cycads and a variety of bushy species).

Gymnosperms, which have been around for at least 383 million years, have exposed reproductive parts, just hanging out there for all to see. But angiosperms evolved to have their bits enclosed in often elaborate flower structures that mature into fruits.

Today, about 9 out of every 10 plants on the seven continents (yes, evenAntarctica has ’em) are angiosperms, ranging from the stinky corpse lily to the dandelions popping up in your yard. Despite their enormous diversity in appearance, life cycle and ecological niche, researchers believe all 225,000-plus species of angiosperms descended from a single ancestor.

Finding that very first “ancestral flower” has been the mission of many a budding paleobotanist. But so far the oldest fossil flowers found have been about 130 million years old, and the handful of examples are already diversified into distinct species.

A New Approach Blooms

Without fossil evidence, researchers turned to another avenue of research: the data crunch.

Reporting today in Nature Communications, a team compiled the world’s largest bouquet of flower trait data points — nearly 13,500 of them from 792 species representing 98 percent of all angiosperm orders (that’s three layers up from species in taxonomic ranking).

That’s one heck of a daisy chain of data.

From all that information on flowers living and fossilized, the researchers used molecular dating to build a chronogram. In other words, they number-crunched a family tree, based on differences between species, which arose through mutations. These mutations occur at a fairly steady rate, so the more differences there are between two species, the further back you’ll find their last common ancestor (LCA).

At the same time, by moving back in time along the lineage, researchers can strip away derived traits — characteristics that arose from those later mutations — and zero in on the traits most likely present in the LCA.

The methods of analysis for this kind of study — and the team used three different approaches — are all complex and may seem a bit brain-numbing to the outsider not immersed in them. (Don’t believe me? Google reversible-jump Markov Chain Monte Carlo Bayesian approach. I’ll wait.)

And quite frankly, getting into the weeds of Bayesian computation is beyond the Dead Things mission. But what is important to understand is that these are tested, respected methods, widely used in the field. The team didn’t pull the first flower out of thin air.

Most importantly, the team’s results created a testable hypothesis for the diversification of the earliest angiosperms that other researchers can now, well, test.

The Root Of It All

According to today’s paper, the ancestral flower was bisexual, with both male and female parts, and had whorl formations of petal-like organs, in sets of three, rather than spiral formations. Perhaps most interestingly, no living species has the same combination of characteristics suggested by the data-driven model. But don’t just take it from me. Today’s paper is open access to all, so dig in and enjoy.

A simplified version of the angiosperm evolutionary tree (Credit HervéSauquet and Jürg Schönenberger)

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Cradles in Rajasthan for India’s unwanted babies

FEATURESINDIA26 DECEMBER 2016

Cradles in Rajasthan for India’s unwanted babies

In a desperate measure, Rajasthan government places cradles around the state where parents can leave unwanted babies.

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Several hundred baby girls are abandoned each year in the Indian state of Rajasthan [Piyal Al Adhikary/EPA]

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Rajasthan, India – In the early morning hours outside a hospital in the city of Bharatpur in Rajasthan, a newborn baby girl – still with her umbilical cord attached – was found abandoned and in critical health. Underweight and wet after hours of intermittent rainfall throughout the night, the baby’s condition deteriorated.

The infant was rushed by hospital staff to a neonatal intensive care unit and then taken to another hospital for better medical treatment. The child welfare committee in Indialodged a police case for the abandonment.

The child is only one of the several hundred baby girls abandoned each year in the Indian state. Poverty, along with the cultural tendency to favour boys, has pushed parents to abandon infants in dumps, hedges, bushes, bus stands, railway tracks, and water bodies – exposing them to fatal risks.

Today, 90 percent of the 11 million abandoned babies in India are girls. In Rajasthan, 674 children were abandoned between 2007 and 2011, highest only after Maharashtra, which saw 1,232 babies deserted.

Cradles for life

To fight the perpetual trend, Rajasthan’s state government introduced the Ashray Palna Yojana project in the 2015-2016 budget. Under the project, 67 cradles were set-up throughout the state – at all district hospitals, medical colleges, and satellite hospitals for the parents to anonymously leave their unwanted babies.

“The main aim of the scheme is to save the newborn babies who are dumped in dustbins and bushes right after birth, most of whom happen to be girls,” says Devendra Agrawal, health department adviser of the scheme.

Once a baby is placed in the cradle, a bell rings three minutes later, informing the hospital staff that a child has been dropped off. The child is then taken to a neonatal intensive care unit and given a medical check-up. Once cleared of any illnesses, the child is then relocated to one of 37 adoption agencies around the state.

READ MORE: Prakash Kaur Bibi: Rescuing India’s abandoned girls

The roadside view of the cradle home built at the adoption agency in Bikaner. One door opens on the roadside to allow parents to leave the babies unnoticed; the babies are then received by adoption authorities once the alarm rings, from a door that opens on the inside of the compound. [Shaifali Agrawal/Al Jazeera]

These adoption centres have been selected by the state for the purpose of caring for these abandoned children. Twenty newborn babies have been received in the cradles since February, when the project was implemented.

The scheme’s credo, “Don’t dump, give them to us” works at multiple levels, believes Agrawal.

“The newborn baby gets a chance to live, and a childless couple gets a reason to live … It keeps the baby girls from falling into the wrong hands,” he says, explaining how many children who are abandoned – if they survive and are not brought to the notice of the police authorities – end up in the network of the illicit trade of child trafficking.

“We tell society if you don’t want a girl, don’t kill her – we will take care of her,” he says. “We are not interested in knowing the identity of the parents; this is a unique feature of this scheme. If we try to track who they are, they wouldn’t leave their babies.”

READ MORE: India’s ‘dark holes’ where millions of girls disappear

Issues at the core

The illegal, yet widespread, practice of dowry, a financial transaction paid to the groom’s family at the time of marriage, is a chief reason parents may consider daughters a financial burden, preferring sons to daughters. This resulted in the practice of sex-selective abortions.

The Indian parliament introduced The Pre-Conception and Pre-Natal Diagnostic Techniques Act (PSPNDT) in 1994, criminalising prenatal sex-determination tests, with an aim to prevent their misuse to selectively abort female foetuses.

The act has been strictly implemented only after 2011, when the gender ratio in Rajasthan for children up to six years fell sharply from 909 for every 1,000 boys in 2001 to 883 in 2011.

“We believe no parent would like to abandon their child, provided there are some circumstances that are so hard for them, which is making them do so … out of sheer helplessness,” says Soha Moitra, regional director of the northern region at Child Rights and You, a nonprofit children’s rights organisation.

“Sometimes, the parents are in a situation where keeping the child with them will badly affect their personal and social life, as in the case of a child born through sexual assault,” believes Kavita Swami, president of an adoption agency in the city of Bikaner that is associated with the project.

In the Indian constitution, it is illegal to abandon or neglect a child, and a parent can be punished for up to seven years in prison and/or fined under Section 317 of the Indian Penal Code, and up to a prison term of three years and/or fine under Section 75 of the Juvenile Justice Act, 2015.

“Since cradle babies are being put in a protective environment of the hospital staff, to be taken care of by adoption agencies, the parents place the babies in cradles legally – with no questions asked. Which is not the case when they abandon a child at unsafe places, say, on the roadside,” says Swami.

The Bikaner adoption agency has put up a cradle in their own ground as well, as an individual step taken to help the kids and the parents.

“The babies received are in very bad condition,” Swami says, explaining how they are “wrapped in some old cloth, the umbilical cord is not cut properly – sometimes they are not even cleaned … It looks like it was pre-decided before birth that they will leave the child, regardless of whether it’s a boy or a girl.”

INSIDE STORY: Can the world be fair to women?

Beyond the cradle

Child rights activists believe making it legal to give up one’s child only absolves parents of their responsibility towards their daughters, without doing anything to address preference for boys in society.

“It is the reaction to symptoms, and not to cause,” says Moitra. “Because it is a quick-fix, the state is actually giving a legitimate sanction for abandonment,” she says.

A similar scheme called Cradle Baby has been operational in the state of Tamil Nadu since 1992, another state where the practice of abandoning girls has been rampant. “We can draw our learnings from the Cradle Baby scheme,” Moitra says.

“It is catastrophic for the children, especially girls. Now, we have several children to be given for adoption, so many adoption agencies come up. But are these agencies registered and regulated?” she asks, speculative about the implementation of the scheme.

“What happens to the child beyond the cradle? One way of looking at it is that the state is giving survival to the child. But is this survival worth it for the child? Most of the time, the places they end up in … are in bad shape with not enough staff, following illegal processes.”

“Is there a complete loop by the state? Can the state ensure a safe and complete childhood?” she asks.

There has been criticism that not enough thought has been put into where the cradles are placed. Some of the hospitals have the cradles in crowded areas, where parents would be reluctant to drop off. Also, some local newspapers reported cases where the bells of some of the cradles are not working, putting the undetected child at risk.

But beyond the logistics of the Ashray scheme, it is generally agreed upon by most of those who spoke with Al Jazeera that more should be done to address the core social issues that give rise to the sense of helplessness that takes hold of parents even before the children are born, including issues of gender roles and how children are socialised from a young age.

Temporary solutions

While parents who abandon children come mostly from a poor background, potential adoptive parents come from all social strata. “We have got requests from a taxi driver to a government employee,” says Swami. There is no income parameter for adopting a child.

“Female infants are being thrown off in dustbins to be eaten by animals. This is a temporary solution to save those lives,” says Agrawal. “The long-term solution to change the mentality would take years. It won’t happen in five to 10 years. We cannot let those girls die till attitudes change,” he adds.

However, Swami says that she notices most pre-adoptive parents ask for girls rather than boys, contrary to popular expectations.

“I am surprised and happy when many parents, especially when adopting their first child, prefer a girl,” she says. “It gives me hope that somewhere society is changing.”

“For the long-term solution, the Rajasthan government and the central government are undertaking several schemes and initiatives for the girl child,” Agrawal adds. For instance, the Dhanalakshmi Scheme by the central government is a conditional cash transfer scheme to families of girls, with an aim to retain her, educate her, and prevent child marriage.

“Every daughter should have the right to live and grow,” Agrawal says. “A future where no daughter is a burden, and no woman helpless.”

Source: Al Jazeera

Posted, but not written by. Louis Sheehan

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The Race to Reveal Antimatter’s Secrets In the shadow of the Large Hadron Collider, six teams are competing to answer one of the Universe’s deepest existential questions

The Race to Reveal Antimatter’s Secrets

In the shadow of the Large Hadron Collider, six teams are competing to answer one of the Universe’s deepest existential questions

CERN’s new antiproton decelerator, ELENA, is set to start slowing the particles down for study this year. Credit:  Dean Mouhtaropoulos Getty Images

In a high-ceilinged hangar at CERN, six rival experiments are racing to understand the nature of one of the Universe’s most elusive materials. They sit just meters apart. In places, they are literally on top of one another: the metallic beam of one criss-crosses another like a shopping-center escalator, its multi-ton concrete support hanging ominously overhead.

“We’re constantly reminded of each other,” says physicist Michael Doser, who leads AEGIS, an experiment that is vying to be the first to discover how antimatter — matter’s rare mirror image — responds to gravity.

Doser and his competitors have little choice but to get cosy. CERN, Europe’s particle-physics laboratory near Geneva, Switzerland, boasts the world’s only source of antiprotons — particles that seem identical to protons in every way except for their opposite charge and spin. The lab’s Antiproton Decelerator is a ring, 182 meters around, that feeds from the same accelerators as the lab’s bigger and more famous sibling, the Large Hadron Collider (LHC). Antiprotons enter the machine traveling close to the speed of light. As the name implies, the decelerator slows the particles down, providing a stream of antiprotons from which experiments must take turns to sip. All this must be done carefully; upon meeting matter, the antiparticles vanish in a puff of energy.

For decades, scientists have worked to pin down antiprotons, and the antihydrogen atoms they can be used to build, for long enough to study. The past few years have seen rapid advances: experimentalists can now control enough antiparticles to start probing antimatter in earnest and to perform increasingly precise measurements of its fundamental properties and internal structure. Jeffrey Hangst, who leads the experiment known as ALPHA, says that in principle at least, his team can now do with antihydrogen anything others do with hydrogen. “For me, this period is what I’ve worked towards for 25 years,” he says.

The experiments have a lot riding on them: even a slight difference between the properties of matter and antimatter could explain why anything exists at all. As far as physicists know, matter and antimatter should have been created in equal amounts in the early Universe and so blasted each other into oblivion. But that didn’t happen, and the origin of this fundamental imbalance remains one of the biggest mysteries in physics.

The CERN efforts are unlikely to crack the case any time soon. Antimatter has so far proved maddeningly identical to matter, and many physicists think it will remain that way, because any difference would shake the foundations of modern physics. But the six experiments, the latest in a line of investigations that began at CERN more than 30 years ago, are attracting attention as the LHC continues to draw a blank in its hunt for particles that could explain the antimatter paradox. Moreover, the teams’ rapid advances in manipulating antimatter have earned them a major upgrade to the facility’s antiproton factory — a cutting-edge decelerator that will start operation by the end of this year and eventually enable experiments to work with up to 100 times more particles (see ‘The decelerators’).

The dozens of physicists working on the CERN experiments know they face a tough challenge. Antimatter is exasperating to work with, the competition between teams is intense and the odds of finding anything new seem low. But CERN’s antimatter wranglers are motivated by the thrill of opening a new window on the Universe. “These are such tour de force experiments that, no matter what answer you get, you can be proud that you do this,” says Hangst. There’s no guarantee that antimatter will yield a major discovery. But “if you can get your hands on some”, he says, “it would be completely reprehensible not to look.”

THE FACT OF THE MATTER

The roots of antimatter physics can be traced to 1928, when British physicist Paul Dirac wrote an equation that described an electron moving close to the speed of light1. Dirac realized that there had to be both a positive and a negative solution to his equation. He later interpreted this mathematical quirk as suggestive of the existence of an anti-electron, now called a positron, and theorized that antimatter equivalents should exist for every particle.

Experimentalist Carl Anderson confirmed the positron’s existence in 1932, when he found a particle that seemed like an electron except that when it traveled through a magnetic field, its trajectory bent in the opposite direction. Physicists soon realized that positrons were routinely produced in collisions: smash particles together with enough energy and some of that energy can turn into matter–antimatter pairs.

By the 1950s, researchers had begun to exploit this energy-to-particle conversion to produce antiprotons. But it took decades to find a way to make enough of them to capture and study. One motivation was the tantalizing idea that antiprotons and positrons could be paired to make antihydrogen, which could then be compared with the well-studied hydrogen atom (see ‘Wrangling antimatter’).

Creating positrons is fairly straightforward. The particles are produced in certain types of radioactive decay, and can be readily caught with electric and magnetic fields. But the higher-mass antiproton is another story. Antiprotons can be made by slamming protons into a dense metal, but they emerge from such collisions moving too fast to be held by an electromagnetic trap.

Antimatter hunters needed a way to massively slow down, or cool, the particles. CERN’s first dedicated attempt to decelerate and store antimatter began in 1982, with the Low Energy Antiproton Ring (LEAR). In 1995, the year before LEAR was slated to be shut down, a team used antiprotons from the facility to produce the first antihydrogen atoms2.

LEAR’s replacement, the Antiproton Decelerator, came online in 2000 with three experiments. Similar to its predecessor, it tames antiparticles, first by focusing them using magnets and then by slowing them using strong electric fields. Beams of electrons also exchange heat with the antiprotons, cooling but not touching them because the particle types are both negatively charged and so repel each other. The overall process slows the antiprotons to one-tenth of the speed of light. That is still too fast to work with, so each of the six experiments uses techniques to further slow and trap the antiprotons.

There is plenty of attrition along the way. Each ‘shot’ of 30 million antiprotons fed to an experiment starts by smashing 12 trillion protons into a target. By the time Hangst’s ALPHA experiment, for example, has slowed its antiprotons enough to pair them with positrons and create antihydrogen, just 30 of the particles remain, the rest having escaped, been annihilated or been discarded because they are too fast or in the wrong condition to study. Experimenting with such tiny numbers of antiatoms is a real pain, says Hangst: “You get a whole new attitude about all the rest of physics when you have to work with this stuff.”

RACE FOR THE PRIZE

Antimatter research at CERN will eventually have some competition from the Facility for Antiproton and Ion Research, a €1-billion (US$1.16-billion) international accelerator complex in Darmstadt, Germany, that will be completed around 2025. But for the moment, CERN has the monopoly on producing antiprotons slow enough to study.

Today, there are five experiments running at the antimatter facility (one, GBAR, is still being built). Each has its own way of working with antiprotons, and although some do unique experiments, they often compete to measure the same properties and independently corroborate each other’s values (see ‘The experiments’).

Credit: Nature Source: CERN

The experiments share one beam, which means that in any two-week period, just three of the five experiments get beam time, each taking their turn in an 8-hour shift. A weekly coordination meeting ensures that each experiment knows when its neighbors’ magnet will be running, so as not to ruin sensitive measurements. But despite the close proximity, teams usually find out about breakthroughs made by their neighbors by reading about them in a paper. “This is built on competition, and that’s good. That motivates you,” says Hangst.

Credit: Nature Source: CERN

Today, only one of the six experiments — BASE — directly studies the antiprotons from the Antiproton Decelerator. BASE holds the particles in a Penning trap, a complex array of electric fields (which pin particles vertically) and magnetic fields (which make them orbit in a circle). The team can store antiprotons for more than a year, and has used the orbits of antiprotons in the trap to determine the particle’s charge-to-mass ratio with record precision3. The group also uses a complex method to reveal the antiproton’s magnetic moment4 — akin to its intrinsic magnetism. The measurement involves switching individual particles rapidly between two separate traps and detecting changes caused by minuscule shifts in an oscillating microwave field. Mastering the technique has become a passion for collaboration leader Stefan Ulmer, a physicist at RIKEN in Wako, Japan. “My entire heart is in this,” he says.

Antihydrogen, which is studied by the other experiments at CERN, comes with its own challenges. Because it has a neutral charge, it is immune to electric fields, and so nearly impossible to control. Experiments must exploit the antiatoms’ weak magnetic properties, restraining the particles with a ‘magnetic bottle’. For the bottle to work, the magnetic fields inside must vary enormously over a tiny distance, changing by 1 tesla — the strength of a car-lifting scrapyard magnet — over just 1 millimeter. Even so, the antihydrogen atoms must have a temperature of less than 0.5 kelvin, or they will escape.

The first antihydrogen atoms, created using antiprotons on the move,lasted about 40 billionths of a second. In 2002, two experiments, ATRAP and ALPHA’s predecessor ATHENA, became the first to slow antiprotons enough to make significant amounts of antihydrogen, amassing many thousands of the atoms each5. The major breakthrough came almost a decade after that, when the teams learned to trap the antiatoms for minutes at a stretch6. They have since measured properties such as charge and mass and used laser light to probe energy levels7. On page 66, ALPHA reports its latest advance: the most precise measurement yet of antihydrogen’s hyperfine structure, the tiny internal energy shifts caused by interactions between its antiproton and positron8.

Together, the CERN experiments explore a range of antimatter properties, any of which could display a difference from matter. The goal for all of them is to keep shrinking the uncertainty, says antimatter veteran Masaki Hori. He leads the ASACUSA experiment, which uses lasers to study antiatoms in flight, free from the disruptive forces of traps. Last year, the team made a precise measurement of the ratio of antiproton mass to electron mass, using exotic helium atoms in which an antiproton takes the place of an electron9. Like other measurements so far, it showed no difference between matter and antimatter. But each result is a more stringent test of whether matter and antimatter really are exact mirror images.

WHAT DIFFERENCE DOES IT MAKE?

If the experiments were to detect any difference between matter and antimatter, it would be a radical discovery. It would mean the violation of a principle called charge, parity and time reversal (CPT) symmetry. According to this principle, a mirror-image Universe that is filled with antimatter and in which time runs backwards will have the same laws of physics as our own. CPT symmetry is the backbone of theories such as relativity and quantum field theory. Breaking it would, in a way, break physics. In fact, only exotic theories predict that the antimatter experiments will find anything at all.

For this reason, the physicists at the LHC tend to view the antimatter researchers next door “with bemused attention”, says Doser, who has been working on antimatter for 30 years. “They think this stuff is fun and interesting, but unlikely to lead to something new,” he says. CERN theorist Urs Wiedemann seems to confirm that. He says that the experiments’ ability to manipulate antimatter is “mind-boggling” and that such tests of theory are essential, but “if you ask is there a firm physics motivation that at some accuracy something new will be discovered, I think a fair statement is, ‘No’”.

Still, the LHC has fared little better in solving the antimatter mystery. Experiments dating back to the 1960s have shown that some physical processes, such as the decay of exotic kaon particles into more familiar ones, have tiny biases in favor of producing matter. LHC experiments have been hunting more such biases, and even a raft of as-yet-undiscovered particles whose behavior in the early Universe could have accounted for the huge matter–antimatter imbalance that remains. There has been good reason to suspect such particles exist: they were predicted by supersymmetry, a theory that was proposed to tie up some troubling loose ends in particle physics. But no such particles have turned up in eight years of searching. Now, the simplest, most elegant versions of supersymmetry — the ones that made the idea appealing in the first place — have been largely ruled out. “Today, the LHC is looking for hypothetical particles, which may or may not be there, with very little guidance from theory. In a way, this is the same situation we’re in,” says Doser.

A few teams are now jumping into the next big challenge: the race to measure antimatter’s acceleration under gravity. Physicists generally expect antimatter to fall just like matter. But some fringe theories predict that it has ‘negative mass’ — it would be repelled by, rather than attracted to, matter. Antimatter with this property might account for the effects of dark energy and dark matter, the identities of which are still unknown. But most mainstream theorists say such a Universe would be inherently unstable.

UP IS DOWN

Measuring antihydrogen in free fall will, as ever, be a question of making it cool enough. Even the tiniest thermal fluctuations will mask the signal of a falling atom. And only neutral particles such as antihydrogen can be used, because even distant sources of electromagnetic fields can expose charged particles to forces bigger than gravity.

Next year, Hangst’s group aims to use proven technology — a vertical version of its ALPHA experiment — to get a definitive determination of whether antimatter falls up or down. “Obviously I think we’ll succeed first, or I wouldn’t get into it,” he says. But two other experiments — Doser’s AEGIS and the antimatter facility’s newest member, GBAR — are hot on the team’s heels. Both use laser-cooling techniques to boost precision, which will enable them to pick up subtler differences between the acceleration of antimatter and matter than ALPHA currently can. AEGIS will measure the bend of a horizontal beam of antihydrogen, whereas GBAR will let its antiatoms free-fall for 20 centimeters. Both aim to bring the antiatoms’ temperature down to a few thousandths of a degree above absolute zero, allowing measurements of gravitational acceleration as sensitive as 1 part in 100, and have plans to go even further.

Later this year, GBAR will be the first to benefit from ELENA, a new 25-million-Swiss-franc ($26-million), 30-meter-circumference ring that sits inside the Antiproton Decelerator and is designed to further slow the antiprotons coming from the machine. Eventually, ELENA will supply particles to all of the experiments, nearly simultaneously. The antiprotons will be slower by a factor of seven and arrive in sharper beams. Because they’ll be more efficiently cooled at early stages, experiments should be able to trap more of the particles.

Now that the teams can manipulate and test antimatter, Hangst says, more and more physicists are becoming interested in the work. They even pitch ideas for experiments and values to check. And the groups are looking outwards, for ways in which their technologies could aid other areas of research. The GBAR team, for example, is working on a portable trap to carry antiprotons to a CERN experiment called ISOLDE, where they can be used to map the neutrons in unstable radioactive atoms.

Assuming a technical impasse doesn’t grind progress to a halt, Doser reckons that by the end of the 2020s, physicists will be adept enough at handling antimatter to be able to replicate a range of atomic-physics feats, including constructing antimatter atomic clocks. “I see lots of ideas popping up now, and that’s a sign the field is moving forward quickly,” he says. “I hope CERN never kicks me out, because I’ve got plans for the next 30 years.”

This article is reproduced with permission and was first published on August 2, 2017.

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How to Be Better at Stress

How to Be Better at Stress

Stress is unavoidable in modern life, but it doesn’t have to get you down. Work, money and family all create daily stress, while bigger issues like politics and terrorism contribute to our underlying stress levels. But approach it the right way, and it won’t rule your life — it can even be good for you. Here are ways to deal with stress, reduce its harm and even use your daily stress to make you stronger.

Take Control

Stress is inevitable; getting sick from it is not.

THE PERCEPTION OF STRESS

While we know that stress is associated with health problems, plenty of people with high-stress lives are thriving. How is that possible? In 2012, researchers from the University of Wisconsin-Madison published a seminal study looking at how 28,000 people perceived stress in their lives. People in the study answered these two questions:

  1. During the past 12 months, would you say that you experienced:
    1. A lot of stress
    2. A moderate amount of stress
    3. Relatively little stress
    4. Almost no stress at all
  2. How much effect has stress had on your health?
    1. A lot
    2. Some
    3. Hardly any
    4. None

The researchers looked at death rates in the study group over eight years. The results are startling. The study found that having a lot of stress in your life was not linked with premature death. But having a lot of stress in your life and believing it was taking a toll on your health increased risk of dying by 43 percent.

CHANGING YOUR PERCEPTION

With stress, the mind and the body are intrinsically linked. You can view stress as something that is wreaking havoc on your body (and it can) or as something that is giving you the strength and energy to overcome adversity. Here’s a quick way to think about these two very different views of stress. Read the statement, and then think about your own reaction to the biological changes that occur during times of stress.

1. When I’m stressed, my body releases adrenalin and cortisol. My heart is beating faster. This means that:

  • Common View: Stress is increasing my risk for cardiovascular disease and heart attack.
  • Alternative View: My heart is working harder and my body is mobilizing its energy to get ready for this challenge.

2. When I’m stressed, my stress response is causing my breathing rate to increase. This means that:

  • Common View: My fast breathing is a sign of anxiety. I worry about how stress is affecting my mental and physical health.
  • Alternative View: I should take a deep breath. My faster breathing means more oxygen is getting to my brain so I can think more clearly.

3. When I’m stressed, blood vessels dilate, causing my blood to flow faster, increasing my blood pressure. This means that:

  • Common View: I can feel my blood pressure rising. This can’t be good for my health.
  • Alternative View: This extra blood flow is fueling my muscles. I’m feeling stronger and ready for the challenge ahead.

It’s probably clear to you that the alternative view is the better choice for thinking about stress. It may be hard to believe that such a small shift in thinking could make a difference, but that’s what Harvard researchers found when they paid 50 study subjects $25 each to take part in a lab experiment designed to induce stress. The test involves giving a talk in front of a group of unfriendly evaluators, followed by a tricky word test. (Researchers have consistently found that this formula of public speaking plus testing in front of a hostile crowd is incredibly uncomfortable and stress-inducing for the poor people who agree to take part in the study.)

Before the social stress test, one group was allowed to play video games; another was taught to simply ignore stressful feelings if they experienced them during the test. But a third group was given advice similar to the quiz above. They got a primer about the physical stress response and were told how a higher heart rate, faster breathing and internal jitters were all tools for making you strong during a stressful event. They were told how the body’s stress response evolved to help us succeed, and that the increased arousal symptoms of stress can aid your performance during times of stress. The bottom line of the lesson was this: In a tough situation, stress make you stronger.

The group that learned to rethink the role of stress in their lives did far better on the test. They gave better speeches and were rated as more confident. They smiled more and had more-positive body language. And physiological indicators showed that their bodies were also managing the stress response better than those of test subjects were taught to ignore stress or given no advice at all.

The Stanford psychologist Kelly McGonigal has been a champion of rethinking stress, noting that the right approach can make you smarter and stronger. Her TED talk on the subject, “How To Make Stress Your Friend,” has been viewed 14 million times.

“What I learned from these studies, surveys and conversations truly changed the way I think about stress,” Dr. McGonigal wrote in her book “The Upside of Stress.” “The best way to manage stress isn’t to reduce or avoid it, but rather to rethink and even embrace it.”

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Practice Stress

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STRESS INOCULATION

The best way to get better at stress is to practice it. Scientists call this “stress inoculation,” and just as exposure to a virus will inoculate you from contracting a virus a second time, regular exposure to small amounts of stress can inoculate you from the most detrimental effects of stress when you suffer a big stressful event in your life.

Stress inoculation has three phases.

1. Education: Learn what to expect. If you need chemotherapy, are experiencing a divorce or have had a setback at work, talk to people who have been through it and learn what to expect going forward so you can be prepared, rather than blindsided, by the stressors ahead of you.

2. Rehearsal: While you can’t rehearse for life’s biggest moments, you can live your life in a way that prepares you for stress. It can be a physical challenge like competing in a triathlon or conquering a mountain. It can be an intellectual stressor like reading your poetry in public or giving a speech. The point is that you need to rehearse stressful situations in order to perform your best under stress.

3. Implementation: When the stressful event hits, you are prepared. You know what to expect and you’ve experienced stressful situations before. You’ve got this.

STILL SKEPTICAL?

Think about how firefighters train. They educate themselves about fire and how it behaves in different situations. They put themselves through grueling physical training to practice carrying heavy equipment, navigating smoky, dark buildings and stairwells, and braving the heat of a raging fire. They practice running into burning buildings. The training is hard and highly stressful.

Now imagine you are out for a nightly walk and you see that a neighbor’s house is on fire. Your heart races. You panic. You fumble with your phone. You take a step toward the house. You hesitate. What do you do? Fortunately, the firefighters arrive and race into the home without hesitation. Your moment of stress and anxiety is just another day at the office for them. They know what to expect. They trained for it.

You can practice for everyday stress in similar ways, by putting yourself in challenging situations. The good news is that practicing stress can actually be enjoyable, even thrilling. The key is to push yourself out of your comfort zone. Here are some suggestions:

  • Run a marathon
  • Play in a Scrabble competition
  • Read an original poem at a poetry slam
  • Climb a mountain
  • Sing karaoke
  • Tell a story in front of a crowd
  • Take on a tough project at work
  • Kayak the Colorado rapids
  • Train to scuba dive
  • Attend a boot camp

Not only will challenging experiences give you more confidence, but the repeated exposure to stressful situations will also change your body’s biological response to stress. Your stress hormones become less responsive, allowing you to better handle stress when it comes.

Dr. Dennis Charney, a psychiatrist and the dean of the Icahn School of Medicine at Mount Sinai in New York City, notes that programs like Outward Bound and basic military training are all designed to make people uncomfortable and build their skills so that they will be better able to handle stress later on. When his children were young, he took them on adventure trips that included “a degree of anxiety” like exposure to wildlife or kayaking in remote areas as a way to build confidence and prepare them to deal with stressful events.Putting yourself or your children in difficult social situations or speaking in public can help adults and children accumulate social and intellectual skills that help in times of stress.

“Live your life in a way that you get the skills that enable you to handle stress,” says Dr. Charney. “Put yourself out of your comfort zone.”

AN RX FOR RESILIENCE

Another factor in how you handle a stressful situation is resilience. The American Psychological Association defines resilience this way:

Resilience is the process of adapting well in the face of adversity, trauma, tragedy, threats or significant sources of stress — such as family and relationship problems, serious health problems or workplace and financial stressors. It means “bouncing back” from difficult experiences.

You can boost your resilience in a number of ways. In the book “Building Resilience: The Science of Mastering LIfe’s Greatest Challenges,” the authors, Dr. Steven M. Southwick and Dr. Charney, studied people who experienced great stressors — prisoners of war, men in the special forces, victims of trauma or survivors of catastrophic events. They found that people with the most resilience in the face of extreme challenges shared several behaviors and mind-sets. From that research, the duo identified 10 factors associated with resilience. You don’t need to practice all 10 behaviors to build resilience; just pick the two or three or four that speak to you.

1. Adopt a positive attitude.

      1. Optimism is strongly related to resilience.

2. Reframe the situation.

      1. Just like the stressed-out study subjects were taught to reappraise stress as their friend, people who are resilient typically reframe a negative situation as an opportunity for growth, learning or change.

3. Focus on core beliefs.

      1. People with a deeply held core belief, strong faith or a commitment to altruism often show more resilience.

4. Find a role model.

      1. Seeing someone else who has come through adversity can strengthen your own resilience.

5. Face your fears.

      1. Confronting a challenge rather than avoiding it will help you cope and build confidence.

6. Fall back on religion or spirituality.

      1. For many people, strong faith or spiritual beliefs can fuel resilience.

7. Seek social support.

      1. People who reach out to friends, family and support groups fare better during stressful times.

8. Exercise.

      1. It improves mood, relieves stress and makes you physically stronger.

9. Inoculate against stress.

      1. Challenge yourself regularly in the areas of emotional intelligence, moral integrity and physical endurance.

10. Find meaning and purpose.

    1. Having a clear purpose in life can boost your emotional strength during difficult times.

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Exercise

Numerous studies have shown us that exercise can improve your mood.

Exercise can channel your stress response into something constructive and distract your mind from the challenges at work or home that make you feel chronically stressed. In many ways exercise appears to be a form of stress inoculation. In studies, mice given access to running wheels and tubes to explore for just two weeks became resistant to stress compared with mice who had not exercised. They measured this by exposing the mice to an aggressive mouse. After the bullying, the exercising-mice bounced back, but the sedentary mice continued to show signs of stress. The bottom line: Exercise doesn’t eliminate stress, but it does give your body the physical conditioning it needs to recover from it.

How Much Exercise Do I Need to Manage Stress?
It doesn’t take much. Even small amounts of exercise can help you manage your stress. The key is consistency. Don’t let the stress of your day push exercise off the schedule.

Does the Type of Exercise Matter?
The exercise that is best for relieving stress is the one you will do consistently. Find something that fits your schedule and that you enjoy. For some, that will be a morning spin class or an evening run. For others, it will be a 30-minute walk at lunch time. A Norwegian study found that people who engaged in any exercise, evan a small amount, reported improve mental health compared with people who never exercised.

What About Weight Training?
One study showed that six weeks of bicycle riding or weight training eased symptoms in women who received a diagnosis of anxiety disorder. The weight training was especially effective at reducing irritability.

Indeed, some research suggests that when it comes to reducing stress, you’ll get more out of exercise if you incorporate some weight training. Studies show that anaerobic or resistance exercises (working with weights) taxes muscles more than aerobic exercise like walking or running. The result is that weight training, done right, may produce more mood-boosting endorphins than cardio exercise. Exercises that stress the large muscles seem to have the biggest effect, like squats, leg presses, incline situps, military presses and bench presses.

Don’t go for a powerlifting record. The best weight training to manage stress consists of three moderate-weight sets of 10 repetitions with one minute of rest. The U.S. Army Research Institute of Environmental Medicine found in a small study that this 3-10-1 moderate weight strategy produced more endorphins than using heavier weights for five reps and a longer rest.

TAKE IT OUTSIDE

Simply taking your exercise outdoors can have a significant effect on your mood.

In a number of recent studies, volunteers who walked outdoors reported enjoying the activity more than those who walked indoors on a treadmill. Subsequent psychological tests showed outdoor exercisers scored significantly higher on measures of vitality, enthusiasm, pleasure and self-esteem and lower on tension, depression and fatigue.

A study last year of older adults found that those who exercised outside did so longer and more often than those working out indoors. The outdoor exercisers averaged about 30 minutes more exercise each week than those who walked or otherwise exercised indoors.

A few small studies have found that people have lower blood levels of cortisol, a hormone related to stress, after exerting themselves outside as compared with inside. There’s speculation, too, that exposure to direct sunlight, known to affect mood, plays a role.

A study in Austria found that almost all the participants reported that the outdoor effort had felt less strenuous to them than their time on the treadmill. And they enjoyed it more.

A small study from the University of Essex found that exercisers exposed to the color green found it easier to exercise and were in a better mood than exercisers exposed to gray or red. (Think green trees versus a cement-walled gym.)

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Mind

Exercise your mind and let it rest to help it better process stress.

GIVING YOUR MIND A REST

For people dealing with high levels of stress, it can be hard to fathom how a few moments of meditation will help. After meditation, the stressors are still there — you’re still getting divorced, caring for an aging parent, struggling with the demands of a high-stress job. How can a few moments of deep thought possibly help your life?

It may help to think about how muscles get stronger. Unrelenting exercise simply tears down a muscle and leads to injury. Smart exercisers know the value of a day of rest — that’s when your muscles regenerate and come back stronger than before.

Now think about your mind as an emotional muscle. Unrelenting stress without a break will not make it stronger. Your emotions, your brain and your body need moments of recovery to get stronger from stress.

“It’s about stress and recovery. Just like you build a physical muscle, just like you build biceps, you have to take the same approach to life stressors,” says Jack Groppel, co-founder of the Johnson & Johnson Human Performance Institute, which offers a course called “The Power of Positive Stress.

Think of meditation like high-intensity interval training (H.I.I.T.) for the brain. During H.I.I.T., you go as hard as you can, then you give yourself a few minutes of recovery before returning to the exercise. This cycle is repeated multiple times and has been shown to be more effective for building strength than long, slow bouts of exercise.

Now imagine a high-intensity, high-stress workday. But every hour, you take two minutes to let your brain recover. “Stress is the stimulus for growth,” says Dr. Groppel. “Recovery is when growth occurs. If there is no recovery, there is no growth. That’s how we build the resilience muscle.”

CONTROLLED BREATHING

Controlled breathing has been shown to reduce stress, increase alertness and boost your immune system. For centuries yogis have used breath control, or pranayama, to promote concentration and improve vitality. The Buddha advocated breath-meditation as a way to reach enlightenment.

Science is just beginning to provide evidence that the benefits of this ancient practice are real. Studies have found, for example, that breathing practices can help reduce symptoms associated with anxiety, insomnia, post-traumatic stress disorder, depression and attention deficit disorder.

Rock and Roll Breathing

When your mind is racing or you feel keyed up, try Rock and Roll breathing, which has the added benefit of strengthening your core.

TRY IT!

MEDITATION

One study recruited 35 unemployed men and women who were seeking work and experiencing considerable stress. All of them participated in stretching exercises, but half of them were also taught formal mindfulness meditation. After three days, everyone said they felt refreshed and better able to withstand the stress of unemployment. Yet follow-up brain scans showed differences in only those who underwent mindfulness meditation. There was more activity, or communication, among the portions of their brains that process stress-related reactions and other areas related to focus and calm. Four months later, those who had practiced mindfulness showed much lower levels in their blood of a marker of unhealthy inflammation than the relaxation group, even though few were still meditating.

To learn more about meditation, try the introductory exercise below.

Basic Mindfulness Meditation

Learn how to pay close attention to the present moment with this meditation exercise.

TRY IT!

WRITE IT DOWN

Another way to cope with stress: writing. It is based on the idea that we all have a personal narrative that shapes our view of the world and ourselves. But sometimes our inner voice doesn’t get it completely right. Some researchers believe that by writing and then editing our own stories, we can change our perceptions of ourselves and identify obstacles that stand in the way of better health. It may sound like self-help nonsense, but research suggests the effects are real.

Timothy D. Wilson, a University of Virginia psychology professor and author of “Redirect: Changing the Stories We Live By,” believes that while writing doesn’t solve every problem, it can definitely help people cope. “Writing forces people to reconstrue whatever is troubling them and find new meaning in it,” he said.

There are a number of methods to tap into the power of expressive writing:

Journal every day.

      1. Just writing about your thoughts, feelings and experiences every day can help. Explore your thoughts and feelings about an issue. Don’t just re-live the stress in your life but try to find meaning in it or explore how well you’ve handled certain situations. Be disciplined and write at the same time every day so it becomes a habit. In a University of Texas study, students who wrote about stressful or traumatic events for four days in a row reaped the benefits for months after. For the next six months, the writing students had fewer visits to the campus health center and used fewer pain relievers than the students in the experiment who wrote about trivial matters.

Change your story.

      1. Use writing to force yourself to confront the changes you need to make in your life. On the first day, write down your goals, then write down why you haven’t achieved them (“I don’t have the time or the money,” “Too many family responsibilities,” etc.) The next day review your writing. Now ask: What is really standing in the way of your goals? Change the story so you have control. Maybe the answer is: I don’t put myself first. I don’t make exercise a priority. I let other people talk me into spending money rather than saving.

Write a mission statement.

    1. People deal with stress better when they have a strong moral compass. This means knowing what you value in life and using that as a guidepost for all decision. By creating a mission statement people can begin to identify the underlying causes of behaviors, as well as what truly motivates them to change. “A mission statement becomes the North Star for people,” says Dr. Groppel. “It becomes how you make decisions, how you lead and how you create boundaries.” To learn more, read our article “Creating a New Mission Statement.”

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Food

STRESS AND YOUR APPETITE

Stress can have a huge impact on your eating habits. During acute stress (the hours after a car accident or the shock of a layoff announcement at work), the stress response can shut down appetite. The fight-or-flight response is designed to suppress hunger — you won’t be effective in battle or run that fast if you are thinking about food. But chronic stress has the opposite effect. Repeated doses of cortisol in your body due to high stress can lead to an increase in appetite.

According to the Harvard Health Letter, gender can play a role in how you eat during times of stress. Some research suggests women are more likely overeat due to stress while men turn to alcohol or smoking. A study from Finland found that obesity was associated with stress-related eating in women, but not in men.

And the reality is that food really can make you feel better during times of stress. So-called comfort food like chocolate cake and ice cream literally blunt the body’s responseto chronic stress. The problem with continuing to self-medicate chronic stress with comfort foods is that it will lead to weight gain and poor health.

Just as you need to reframe your view of stress and exercise and meditate to give your body a break from stress, you can also adopt strategies to use food to help you better cope with stress.

MINDFUL EATING

During times of stress, we can be particularly careless about what we eat and resort to mindless snacking, grabbing sweets from the office treat table or eating bags of junk food on the run. During times of stress, it’s particularly important to engage in “mindful eating,” which involves eating slowly and relishing every bite.

HOW TO EAT MINDFULLY

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“The question isn’t what are the foods to eat, in my mind,” says Dr. Michael Finkelstein, a holistic physician who oversees SunRaven, a holistic-living center in Bedford, N.Y. “Most people have a general sense of what the healthy foods are, but they’re not eating them. What’s on your mind when you’re eating: That’s mindful eating to me.”

Here’s a simple exercise to try next time you are sitting down to a delicious meal:

  1. Place a forkful of food in your mouth. Make it something you love.
  2. Put the fork down and resist the temptation to take a second bite.
  3. Chew slowly. Tune in to the texture of the food, the flavor, the aroma. Focus on the colors on your plate.
  4. Be present in the moment and think only about the food in your mouth. Reflect on the effort that went into growing or producing this food; the effort it took to prepare this meal.
  5. Savor the moment.

To learn more, read “Mindful Eating as Food for Thought.”

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Support and Relationships

LEAN ON LOVED ONES

The pressure of family responsibilities is one of the most common forms of stress. But during times of stress, our friends and family members are most likely to give us the support we need to get through it.

One of my favorite friendship studies involved a steep hill, a heavy backpack and 34 university students. Students were fitted with a backpack full of free weights equivalent to 20 percent of their body weight. They stood at the base of a hill on the University of Virginia campus with a 26-degree incline. Wearing the heavy backpack, they had to imagine climbing that hill and guess the incline. When a student stood alone, he or she tended to guess that the hill was very steep. But when they stood next to a friend, the hill didn’t look as daunting. Overall, students in pairs consistently gave lower estimates of the hill’s incline compared with students who were alone. And the longer the friends had known each other, the less steep the hill appeared.

The lesson: The world does not look as challenging with a friend by your side.

For people who study stress, the role of friendship, family and support networks can’t be overstated. Time and again research shows that social support is a defining element in our happiness, quality of life and ability to cope with stress.

MAP YOUR SOCIAL NETWORK

During times of high stress we have a tendency to retreat. We cancel social plans and focus on the work, money crisis or trauma that is our source of stress. But friends and social support are among the best forms of therapy to help you escape stress for brief periods of time. Friends can also make you feel better about yourself, and that mountain of stress in your life won’t look so steep.

When Dr. Southwick co-wrote his book on resilience, he interviewed a number of people who had shown resilience against all odds, including former prisoners of war and people who had survived trauma. One thing they had in common was social support.

“The resilient people we interviewed actively reached out for support,” said Dr. Southwick. “They don’t sit around and wait.”

Even POWs held in isolation devised a tapping method of communication with their fellow prisoners. “Most, if not all, said it was life-saving to know they weren’t alone and they were cared for,” said Dr. Southwick.

When Dr. Southwick, a psychiatrist, meets with a new patient, one of the first things he does is construct a diagram of the patient’s social network. Sometimes they just talk about it; some patients want to map it out on paper. “Who is in your life? Who can you count on?” asks Dr. Southwick. Make your own list of your social network and keep it handy when you need to call on someone for support.

DON’T JUST SEEK SUPPORT, GIVE IT

If you lead a highly stressful life, the solution may be to add one more task to your daily to-do list. Give back.

Research consistently shows that helping other people and giving social support is a powerful way to manage the stress in your life and boost your resilience. Volunteer work, mentoring, mowing your elderly neighbor’s lawn, listening to a friend who is struggling — all these can enhance your own ability to manage stress and thrive.

“Time spent helping others, sharing our knowledge and providing social and emotional support gives meaning and purpose to our lives,” said Adam Grant, a Wharton management professor and co-author of the book “Option B: Facing Adversity, Building Resilience and Finding Joy” with Sheryl Sandberg. “Getting out of yourself and helping others that may be even more powerful than receiving social support.”

REACH OUT AND TOUCH SOMEONE

The simple act of touching another person — or being touched — can ease your stress. James A. Coan, an assistant professor of psychology and a neuroscientist at the University of Virginia, recruited 16 women who felt they had strong support in their relationships. To simulate stress, he subjected each woman to a mild electric shock under three conditions, all while monitoring her brain. The shocks were administered in no particular order while the woman was 1) alone, 2) holding a stranger’s hand, and 3) holding her husband’s hand.

Notably, both instances of hand-holding reduced the neural activity in areas of the woman’s brain associated with stress. But when the woman was holding her husband’s hand, the effect was even greater, and it was particularly pronounced in women who had the highest marital-happiness scores. Holding a husband’s hand during the electric shock resulted in a calming of the brain regions associated with pain similar to the effect brought about by use of a pain-relieving drug.

Coan says the study simulates how a supportive marriage and partnership gives the brain the opportunity to outsource some of its most difficult neural work. “When someone holds your hand in a study or just shows that they are there for you by giving you a back rub, when you’re in their presence, that becomes a cue that you don’t have to regulate your negative emotion,” he told me. “The other person is essentially regulating your negative emotion but without your prefrontal cortex. It’s much less wear and tear on us if we have someone there to help regulate us.”

ANIMALS CAN HELP

Spending time with your pet can offer a temporary reprieve from stress. Spending time with your dog and taking it for a walk is a twofer — you get the stress reduction of a pet plus the stress-busting benefits of a walk outdoors.

The evidence that pets are a source of comfort and stress relief is compelling. At Veterans Affairs hospitals, therapy animals including dogs and parrots have helped patients undergoing treatment for post-traumatic stress reduce their anxiety.

Studies have shown that after just 20 minutes with a therapy dog, patients’ levels of stress hormones drop and levels of pain-reducing endorphins rise.

In a controlled study of therapy dog visits among patients with heart disease, researchers at the University of California, Los Angeles, found a significant reduction in anxiety levels and blood pressure in the heart and lungs in those who spent 12 minutes with a visiting animal, but no such effect occurred among comparable patients not visited by a dog.

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Health

Excessive stress can take a physical toll if it’s not managed correctly.

While some stress is essential for human function, chronic stress creates a cascade of physical changes throughout your body.

Heart: During a stressful event, your heart rate increases and your body releases the stress hormones — cortisol, adrenaline and noradrenaline. The blood vessels that serve the heart dilate, increasing blood pressure. Normally the effects are temporary, but in people with chronic stress, the effects on the heart are unrelenting, raising the risk for high blood pressure, heart attack and stroke.

Immune System: Chronic stress can depress the immune system and make you more vulnerable to colds or more serious illnesses.

Diabetes Risk: During stress, the liver increases glucose production for a boost of energy to propel you during an emergency. Chronic stress can lead to extra blood sugar, increasing risk for diabetes, especially among those already at high risk, such as the overweight or those with a family history of the disease. According to the American Psychological Association, learning to manage your stress can be nearly as effective at controlling blood sugar as medication.

Stomach and Digestion: Stress can affect how fast food moves through your body, stomach acid and the absorption of nutrients. Chronic stress can also lead to overeating or alcohol use. All of these factors can contribute to a number of gastrointestinal issues including acid reflux, heartburn pain, nausea, stomach pain, ulcers and diarrhea.

Sex and Reproduction: In men, chronic stress can affect testosterone levels and sperm count, and contribute to erectile dysfunction. In women, stress can create irregular menstrual cycles and painful periods and exacerbate premenstrual syndrome. Stress can also worsen the symptoms of menopause, including more frequent and more severe hot flashes. In both men and women, chronic stress can dampen sexual desire.

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About the Author

Tara Parker-Pope is the founding editor of Well, an award-winning consumer health site with news and features to help readers live well every day.
Posted, but not written by, Louis Sheehan
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9 things you (probably) didn’t know about Dunkirk

9 things you (probably) didn’t know about Dunkirk

In 1940, as British troops retreated through France under fire from an advancing German Army, a massive evacuation was launched to bring the soldiers safely home. Between 26 May and 4 June 1940, a mammoth 338,000 troops were rescued from the beaches of Dunkirk, France, in the remarkable Operation Dynamo.

Ahead of the release of Christopher Nolan’s Dunkirk in UK cinemas this weekend, military historian James Holland shares some lesser-known facts about the evacuation, and the fighting that led up to it…

Charles Cundall’s painting ‘The Withdrawal From Dunkirk, June 1940’. (IWM via Getty Images)

1) Britain had the only 100% mechanised army in 1940

Britain in the early years of the war has often been perceived to have been full of Blimpish commanders, out-of-date equipment and antiquated, stuck-in-the-mud tactics.
In fact, the British Army’s equipment in 1940 was certainly a match for that of the Germans. The Bren light machine-gun did not have the rate of fire of the German MG34, but was solid, accurate, and more dependable than its far friskier German rival. Meanwhile, the new British uniforms were the most modern in the world at the time, and unlike anything any soldier had worn before. The British Expeditionary Force (BEF) was also entirely mechanised, which was certainly not the case for the German Army. In fact, of the 135 German divisions used in the attack in the West, only 16 were mechanised; the other 119 used horses and their soldiers’ own two feet. British tanks were mostly superior to those of the German Army too, and while they had not invested as heavily in radio as the Germans, the BEF still had proportionally considerably more radio sets than the French.

Members of the British Expeditionary Force (BEF) withdraw to England from Dunkirk. (Getty Images)
The reason for defeat in France in 1940 was not a failure in equipment, tactics or training, but the BEF’s small size: just 10 divisions. This meant they could only ever play a supporting role in the action. When Belgian and French forces on their flanks collapsed, the BEF had no choice but to fall back in line with their allies. For Britain, an island nation with a large seaborne empire, the Royal Navy was the senior service. Pre-war rearmament had sensibly focussed on naval and air power. After all, France was an ally with a vast army. The idea was that Britain would take the lead at sea, France on land, and both would contribute to air power.

2) There were no telephones at French Army headquarters

Until he was fired on 19 May (following the catastrophic collapse of the Meuse Front), General Maurice Gamelin was commander-in-chief of all French and British forces in France. He was also the overall architect of plans to defeat any German attack. Gamelin firmly believed any future war would be much like the previous one of 1914-18: long, drawn-out and largely static war of attrition.
He was half-right, or half-wrong, depending on which way one looks at it. The Second World War lasted longer than the First World War. While it was a war of attrition in many ways, it was not static. The German approach was always to try and win battles and wars swiftly and with considerable skill of manoeuvre. This was a strategy forced upon them by their fundamental lack of resources. In this regard, little had changed since the days of Frederick the Great. By the Second World War, however, Germany had harnessed radio technology to these age-old principles to very great effect.

French General Maurice Gamelin studying a map of Europe in around 1939. Gamelin was “repeatedly and fatally out of touch with his commanders,” says James Holland. (Getty Images)
In contrast, the French had largely eschewed radio technology in favour of landline telephones and traditional dispatch riders. At his headquarters on the edge of Paris, Gamelin insisted there should be no telephones at all, such was his paranoia of a security break. This meant he was repeatedly and fatally out of touch with his commanders at a time when swift and rapid decision-making was essential. With German artillery and the Luftwaffe also repeatedly cutting phone lines, the French were ever more dependent on dispatch riders, who were forced to battle through roads clogged with refugees. Often they became lost, took too long, or failed to return altogether. Inevitably, the French Army ground to a halt, unable to move or respond to the rapidly unfolding situation.

3) The Luftwaffe’s worst day

It is widely accepted that the Germans had it pretty much their own way from the moment they launched Case Yellow (the invasion of France and the Low Countries) on 10 May 1940. Spearheading the attack and apparently ruling the skies was the Luftwaffe, with its mix of screaming Stuka dive-bombers, Messerschmitt fighters and Heinkel and Dornier medium bombers.
However, that first day of the campaign was the worst the Luftwaffe suffered for some three years. A staggering 353 German planes crashed or were shot down. (To put that in perspective, the worst day for the Luftwaffe in the battle of Britain saw them lose 67 aircraft). Most were transports bringing in airborne troops, but these Junkers 52s had only been brought to bear by scouring training schools and their losses severely set back aircrew training. In fact, the Luftwaffe had still not made good on its losses by the time they invaded the Soviet Union the following June.

4) The chance discovery of the ‘east mole’

The Senior Naval Officer tasked with overseeing the shore end of the Dunkirk evacuation was Captain Bill Tennant. Tennant arrived on the afternoon 27 May, and had been told they might be able to evacuate 45,000 troops if he were lucky. The harbour facilities had been smashed and the port’s quays were unusable, so Tennant signalled back to Dover asking for every available craft, no matter how small, to sail to Dunkirk to help lift men from the beaches.
Getting men onto boats and ships direct from the beaches was an incredibly slow and laborious process. The situation looked bleak. Later that same evening, though, Tennant noticed the Luftwaffe had not hit the two long moles [wooden breakwaters] that extended some 1,600 yards out into the sea. There was no obvious way of reaching the western mole across the harbour’s mouth, but the eastern mole began from the harbour wall and was easily accessible. Made of latticed concrete piles and topped by a narrow wooden walkway, it was a breakwater rather than a jetty. While at first glance it looked as though it was not strong enough to take a moored ship alongside, Tennant felt there was nothing to lose from trying. The cross-Channel steamer, Queen of the Channel, was called to test it and after gently nudging her stern against the concrete piles, managed to drift alongside. The mole withstood this strain without any obvious difficulty.

British and French troops waiting on the dunes at Dunkirk to be picked up and taken back to England. (Getty Images)
A lifeline had been discovered and over the next five days and nights, the eastern mole not only remained intact but also undamaged by either the sheer weight of ships mooring alongside or by enemy bombs. Of the 338,226 men lifted from Dunkirk, 239,555 – the vast majority – were taken from the eastern mole.

5) The battle of Britain began over Dunkirk

Officially, the battle of Britain began on 10 July 1940. (This was the date given by Hugh, the commander-in-chief of RAF Fighter Command. Yet as Dowding admitted, as far as he was concerned, it began the day Britain entered the war.)
However, RAF Fighter Command was created to defend Britain and first entered the fray over Dunkirk and the Pas de Calais on 20 May 1940. The Luftwaffe had been given a lead role in preventing the evacuation and Fighter Command more than played their part in ensuring German air forces failed in their task. Few on the ground saw them as the sky was filled with low cloud. Thick, black smoke from burning oil storage tanks rose to some 15,000 feet and spread across the entire area. They were there, nonetheless, and managed to shoot 326 enemy aircraft during the operation, while losing of 121 of their own.

A British ship rescues soldiers from a sunken landing craft. (Getty Images)

6) The truth about Hitler’s halt order

On 24 May, Hitler issued his infamous order for his panzer divisions [armoured tank divisions] to halt, denying them the chance to completely encircle the retreating British Expeditionary Force. Ever since the order, there has been speculation as to Hitler’s motives. It has even been suggested that he wanted to give the British a chance to escape.
The truth is more straightforward, and underlines Hitler’s utter ineptitude as a military leader. After all, he never went to staff college [to train as a military officer] and was ill qualified to be making high-level military decisions in almost every regard.
The initial halt order was issued by General von Kleist on 23 May. He did not understand new mobile panzer tactics and feared his armoured tank divisions were getting too far ahead of the foot-slogging infantry. This order – which was to be in place for 24 hours – was reinforced by Field Marshal von Rundstedt. When General Halder, army chief of staff, heard about the order, he immediately rescinded it and furthermore transferred all panzer divisions to rapidly close in on Dunkirk from the north. Von Rundstedt, piqued to have been humiliated by Halder, complained to Hitler.
Hitler, who had been told nothing of all this beforehand, exploded with anger. He hated the Prussian military elites, and was deeply suspicious of the army leadership. Clearly, they needed to be taught a lesson. He immediately countermanded all Halder’s decisions and gave the authority to lift the halt order back to von Rundstedt. Logical military thinking played no part in Hitler’s decision, rather, it was motivated by a determination to show who was boss and stamp his authority on his subordinates. But in so doing, Hitler very possibly lost the war.
Britain’s army may have been small in 1940, but on 27 May, the country came its closest to defeat. Foreign secretary Lord Halifax and new prime minister Winston Churchill argued over whether Britain should put out peace feelers. Halifax briefly threatened to resign, which almost certainly would have brought down the government. Churchill insisted that even putting out feelers would be crossing a Rubicon from which there could be no return. He won the day, but had the BEF been lost, the outcome may well have been very different. The halt order was not lifted until late on 26 May, and no panzers began moving again until the following morning – by which time the perimeter at Dunkirk had been secured and the evacuation had begun.

7) The rescue of an England cricket captain

Among those rescued at Dunkirk was former England cricketer, Douglas Jardine, who had captained the national side back in 1932-3. Jardine had retired from cricket in 1934, and although he was a qualified lawyer, made his living from journalism and writing. In August 1939 he joined the Territorial Army and then was commissioned into the Royal Berkshire Regiment on the outbreak of war a few weeks later. He was then sent to France with the BEF. Jardine served well, but was wounded in fighting near Dunkirk. He became separated from most of his men, making him among the last in his battalion to be lifted. Ironically, the ship that took him home was a destroyer called the HMS Verity. Jardine’s greatest friend during his England cricketing days had been the Yorkshire bowler, Hedley Verity, who had even named his son Douglas after his friend. Verity was less lucky – he was mortally wounded in Sicily in July 1943 leading his company in an assault on German positions.

Douglas Jardine, a former England cricket captain who was rescued from Dunkirk. (Getty Images)

8) The last British soldier to leave Dunkirk

The last British soldier to leave Dunkirk was not a member of the rank and file but rather Major-General Harold Alexander. Alexander had taken over as acting commander of the BEF on 31 May. His imperturbability was legendary, and he was given the task of overseeing the last stages of the evacuation.
The last British troops began boarding at around 9pm on Sunday 2 June. By this time, the perimeter had collapsed. Although French troops were still heroically defending the town, German artillery was raining down on the harbour. At 11.30pm, Alexander, along with Captain Bill Tennant, boarded a motor launch and began a last tour of the harbour and then the length of the beaches as far as Bray Dunes, calling out to any last remaining troops. They heard no replies; all that remained were the silhouettes of abandoned vehicles. Satisfied they had fulfilled their task, they signalled, “BEF evacuated. Returning now”. Then they, too, set sail for England.

9) Many British vehicles abandoned at Dunkirk ended up in Russia

Although not a single British soldier was left on the Dunkirk beaches, some 70,000 troops were left behind in France, either dead, wounded, prisoner or still stuck further south. The British also left behind 76,000 tons of ammunition, 400,000 tons of supplies and 2,500 guns. On top of that, a staggering 64,000 vehicles were abandoned. This was a salivatingly large number for the vehicle-short Germans. Although many of those left at Dunkirk had sand poured into the radiators and fuel tanks, a large proportion were salvageable and were used again.

Abandoned equipment at Dunkirk. Around 64,000 vehicles were left behind. (Getty Images)
In fact, many of them went on to provide sterling service to the Wehrmacht and a large number ended up crossing into the Soviet Union a year later as part of the German invasion, Operation Barbarossa. By then, the German Army was using some 2,000 different vehicles, all of which required different parts, from gaskets and distributors to fuel pumps. Needless to say, of those British vehicles that did make their way to the USSR, very few ever headed west again.
James Holland is a historian, bestselling author, and broadcaster. He is currently writing a three-volume new history of the Second World War in the West. Volume 2: The Allies Fight Back was published in May 2017.
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Hamburg Is Ready to Fill Up With Hydrogen. Customers Aren’t So Sure.

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The Coradia iLint, a hydrogen-powered regional train built by Alstom, being refueled in Salzgitter, Germany. CreditGordon Welters for The New York Times

HAMBURG, Germany — With its sleek architecture, the gas station in this city’s famous warehouse district hints at the future of fueling.

A small laboratory with tubes and tanks, turbocharged with electricity, stands in place of the usual cash registers and snacks. Two stark white pumps are ready to dispense hydrogen, a clean fuel without the climate-harming emissions of gasoline or diesel.

All the place lacks is customers. On a recent spring day, the only people using the pumps were employees, learning to fill the company car.

A Swedish energy company, Vattenfall, built the station at a cost of 6 million euros in 2012, anticipating growing numbers of hydrogen-powered cars, and especially buses, that would guzzle large volumes of the fuel. But hydrogen is still stuck in the prototype stage, struggling with high costs, competition from electric vehicles, and worries, perhaps exaggerated, about the risks.

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“We try not to have lunch here or have guests stay too long,” Arne Jacobsen, a Vattenfall business development manager, said in a room where hydrogen gas was stored in pressurized tanks. Hydrogen can be volatile if it escapes into the air.

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Lutz Wiese of Vattenfall fueling a hydrogen-powered car in Berlin. Only about 260 passenger cars on German roads are powered by hydrogen fuel cells. CreditThomas Peter/Reuters

The filling station in Hamburg, part of several bets on hydrogen in this German port city, reflects the great appeal, and challenge, of this clean fuel.

Under the technology, hydrogen gas runs through a fuel cell. There, the gas is mixed with oxygen, a process that generates an electric charge to power the vehicle. The only emission produced is water vapor.

Hydrogen vehicles also offer advantages over battery-powered counterparts. They have a longer range and can be refueled quickly, like a gasoline or diesel vehicle.

As the United States retreats from its global leadership role on climate change, countries like Germany are aggressively moving ahead, testing all manner of clean energy initiatives. The German government, along with private companies like Royal Dutch Shell, Daimler and the industrial gas giant Air Liquide, has invested about €1.4 billion over the past decade to nurture the development of hydrogen vehicles.

In Hamburg, Germany’s second-largest city and busiest port, the money has helped build a small network of filling stations, encouraged road trials of hydrogen-powered city buses, and funded research. Daimler is planning to introduce a hydrogen-powered S.U.V. this year.

But the financial support has not yet translated into commercial success.

Germany has only about 260 passenger cars on the roads, and 16 buses, that are powered by hydrogen fuel cells. By comparison, there are about 55,000 battery and plug-in hybrid cars across the country.

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The Coradia iLint train on a test run in March. CreditGordon Welters for The New York Times

This year, hydrogen faced a big setback, when Toyota, one of the largest producers of such vehicles, recalled all of its Mirai hydrogen-powered cars. Although Toyota continues to back hydrogen vehicles, other big automakers are increasingly betting on electric cars.

“We do see some expectations that were not met,” said Klaus Bonhoff, head of the National Organization Hydrogen and Fuel Cell Technology, which manages the government’s programs involving the fuel. Despite the disappointments, Mr. Bonhoff said that the government was likely to continue supporting hydrogen because more than one technology would be needed to reduce emissions.

As much as anywhere in Germany, Hamburg, a graffiti-festooned center of youthful and commercial cool, has thrown its weight behind hydrogen and other clean energy technologies.

The regional authorities want to reduce air pollution from the growing volumes of traffic on the roads and from smoke-belching cruise liners and other ships in the port, while at the same time stimulating business and jobs based on clean energy. In another green wrinkle, making hydrogen on a large scale could soak up excess electricity produced by the many wind farms near Hamburg.

While some of these efforts are a long way off, one project, a commuter train, is close to fruition. This year, the hydrogen-powered train took its first test through the woods, running about 50 miles an hour. When done, it could go up to 85 m.p.h.

“This is our baby,” said Stefan Schrank, the prototype project manager for Alstom, the train’s French manufacturer. “We are very proud.”

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The Coradia iLint is powered by fuel cells at the top of the train. CreditGordon Welters for The New York Times

The company is trying to find a role for the gas that makes economic sense.

About 40 percent of Germany’s rail network is not electrified. And Alstom executives say that it would be cheaper to replace the diesel-powered trains with hydrogen vehicles than to string electric lines along the tracks.

Alstom says it has preliminary orders for 50 to 60 trains from German regional authorities. If the orders are fulfilled, Mr. Schrank estimated the project would break even, based on the investments by Alstom and the German government, which has put in €8 million ($8.9 million).

A commuter line like this one looks well-suited to hydrogen. The company can build a fuel supply system in a safe place like a rail yard of its choosing.

“Every night we know where the train is coming,” Mr. Schrank said. “We can fill it.”

Using hydrogen on an airplane, which would need to fly all over the world, would be trickier. Airbus has experimented with using hydrogen to power a plane’s emergency electrical systems and when it is on the ground, potentially a big pollution reducer.

But Airbus is reluctant to install these systems on a large number of planes until there is a worldwide network of fueling facilities. “Our aircraft do go to some very remote places,” said Barnaby Law, the company’s project director for hydrogen and fuel cells, who is based in Hamburg. “It has to be economically feasible.”

Even a car or bus network is challenging. Hamburg has four hydrogen filling stations — which are enough, provided that a motorist is careful.

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The Coradia iLint in Salzgitter during its March test run. The train has an estimated top speed of 85 miles per hour. CreditGordon Welters for The New York Times

The price, too, is proving prohibitive. Hydrogen passenger cars can cost nearly double their electric counterparts.

The city’s bus operator, FFG, which is required in the coming years to shift to buses with zero emissions, is testing six partly hydrogen-powered buses as part of a low-polluting trial fleet of about three dozen vehicles. The buses are essentially custom built, costing about four to six times the price of a diesel-powered bus, according to Philip Thetens, a vehicle technology executive at FFG. And they are prone to breakdowns that can be difficult to fix.

The technology also faces a perception problem stretching back to the Hindenburg air disaster in 1937, when a hydrogen-filled airship exploded in New Jersey. Industry executives say that they have developed equipment and procedures to make the handling of hydrogen safe.

“There is so much disinformation about hydrogen,” said Thomas Bystry, who is in charge of the hydrogen filling stations in Germany at Royal Dutch Shell. Shell says that hydrogen is no more dangerous than gasoline.

Companies like Shell and Airbus chalk up the difficulties to the technology being in its infancy. They are planning out decades for new products.

“If you look back 100 years, we had horse carriages and steam engines,” said Mr. Law of Airbus. “There is no future fuel without pain.”

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In Neanderthal DNA, Signs of a Mysterious Human Migration

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Part of a femur, or thigh bone, from a Neanderthal that was discovered in the Hohlenstein-Stadel cave in Germany. CreditOleg Kuchar/Museum Ulm

With fossils and DNA, scientists are piecing together a picture of humanity’s beginnings, an origin story with more twists than anything you would find at the movie theater.

The expert consensus now is that Homo sapiens evolved at least 300,000 years ago in Africa. Only much later — roughly 70,000 years ago — did a small group of Africans establish themselves on other continents, giving rise to other populations of people today.

To Johannes Krause, the director of the Max Planck Institute for Human History in Germany, that gap seems peculiar. “Why did people not leave Africa before?” he asked in an interview. After all, he observed, the continent is physically linked to the Near East. “You could have just walked out.”

In a study published Tuesday in Nature Communications, Dr. Krause and his colleagues report that Africans did indeed walk out — over 270,000 years ago.

Based on newly discovered DNA in fossils, the researchers conclude that a wave of early Homo sapiens, or close relatives of our species, made their way from Africa to Europe. There, they interbred with Neanderthals.

Then the ancient African migrants disappeared. But some of their DNA endured in later generations of Neanderthals.

“This is now a comprehensive picture,” Dr. Krause said. “It brings everything together.”

Since the 1800s, paleontologists have struggled to understand how Neanderthals are related to us. Fossils show that they were anatomically distinct, with a heavy brow, a stout body and a number of subtler features that we lack.

The oldest bones of Neanderthal-like individuals, found in a Spanish cave called Sima de los Huesos, date back 430,000 years. More recent Neanderthal remains, dating to about 100,000 years ago, can be found across Europe and all the way to southern Siberia.

Then, 40,000 years ago, Neanderthals vanish from the fossil record.

As a graduate student in the mid-2000s, Dr. Krause traveled to museums to drill bits of bone from Neanderthal fossils. In some of them, he and his colleagues managed to find fragments of DNA that they could study.

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Excavations at the entrance of the Hohlenstein-Stadel cave in 1937, the year when the Neanderthal femur was found. CreditMuseum Ulm

Scientists who study ancient genes search for two kinds of genetic material. The vast majority of our genes are in a pouch in each cell called the nucleus. We inherit so-called nuclear DNA from both parents.

But we also carry a small amount of DNA in the fuel-generating factories of our cells, called mitochondria. We inherit mitochondrial DNA only from our mothers, because a father’s sperm destroys its own mitochondrial DNA during fertilization.

Years ago, Dr. Krause and his colleagues started their search for ancient Neanderthal genes in a fossil by looking for mitochondrial DNA. After discovering mitochondrial DNA in some fossils, they later managed to find nuclear DNA.

The genes held some surprises. For example, bits of DNA in living people of non-African ancestry come from Neanderthals. When modern humans expanded out of Africa, they seem to have interbred several times with Neanderthals.

Those children became part of human society, passing on their genes.

But a finger bone and a tooth from a Siberian cave called Denisova left Dr. Krause and his colleagues with a baffling puzzle.

Inside those fossils, the scientists found sequences of mitochondrial DNA that were not human or Neanderthal, but something else — a distant branch of the family tree. The Neanderthal mitochondrial DNA was much closer to our own.

Later, the researchers managed to recover the nuclear DNA from the Denisovan finger bone, which showed Denisovans and Neanderthals were more closely related to each other.

As scientists found ancient DNA in more fossils, our history has come into sharper focus. Scientists now estimate that the common ancestor of modern humans, Neanderthals and Denisovans, lived between 765,000 and 550,000 years ago.

About 445,000 to 473,000 years ago, that common ancestor’s descendants split into two lineages. One eventually led to modern humans, while the other led to Neanderthals and Denisovans.

After years of investigation, however, Dr. Krause still did not understand why the nuclear DNA and mitochondrial DNA of Neanderthals seemed to have different histories. The former pointed to a link with Denisovans, the latter to humans.

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The entrance to the Hohlenstein-Stadel cave seen recently. In 2013, a researcher examined a Neanderthal fossil from the cave and was able to reconstruct all of its mitochondrial DNA. CreditWolfgang Adler/Museum Ulm

The mystery only deepened in 2013. Another team of researchers retrievedmitochondrial DNA from a Neanderthal-like fossil at Sima de los Huesos, dating back 430,000 years.

The researchers had expected the DNA to resemble that of later Neanderthals in Europe. Instead, the mitochondrial DNA looked like it belonged to Denisovans — even though the Denisova cave was 4,000 miles away in Siberia.

Last year, the researchers announced they had gathered a small fraction of the nuclear DNA from the same Sima de los Huesos fossil. That genetic material looked like it belonged to a Neanderthal, not a Denisovan.

Dr. Krause and his colleagues have now discovered new Neanderthal DNA that they believe can solve the mystery of this genetic mismatch.

In 2013, one of Dr. Krause’s graduate students, Cosimo Posth, examined a Neanderthal fossil from a German cave called Hohlenstein-Stadel. He was able to reconstruct all of its mitochondrial DNA.

Dr. Posth estimated that the Neanderthal fossil was 120,000 years old and, more important, that it belonged to a branch of the Neanderthal family tree with a long history. He and his colleagues determined that all known Neanderthals inherited their mitochondrial DNA from an ancestor who lived 270,000 years ago.

All the data pointed to a sequence of events that could solve the puzzle that had bedeviled Dr. Krause for so long.

The common ancestors of Neanderthals and Denisovans spread across Europe and Asia over half a million years ago. Gradually the eastern and western populations parted ways, genetically speaking.

In the east, they became Denisovans. In the west, they became Neanderthals. The 430,000-year-old fossils at Sima de los Huesos — Neanderthals with Denisovanlike genes — capture the early stage of that split.

At some point before 270,000 years ago, African humans closely related to us moved into Europe and interbred with Neanderthals. Their DNA entered the Neanderthal gene pool.

MORE REPORTING ON HUMAN ORIGINS

  • Siberian Fossils Were Neanderthals’ Eastern Cousins, DNA RevealsDEC. 23, 2010

  • Lost in a Million-Year Gap, Solid Clues to Human OriginsSEP. 18, 2007

  • Palm-Size Fossil Resets Primates’ Clock, Scientists SayJUNE 06, 2013

  • New Fossils Indicate Early Branching of Human Family TreeAUG. 09, 2012

Over many generations, most of that new DNA disappeared. But the mitochondrial DNA survived, passed down from mothers to their children. In fact, eventually all the Neanderthals inherited it, for some reason discarding the mitochondrial DNA that the species once had.

Dr. Posth said it was possible that early members of our own species moved from North Africa into Europe. Supporting this idea was the discovery reported last month of fossils of Homo sapiens in Morocco dating back 300,000 years.

But Dr. Posth said it was too soon to rule out another possibility: that these migrants belonged to another species in Africa closely related to us that scientists have yet to document.

“I feel uncomfortable to give a name to these humans,” Dr. Posth said.

Adam C. Siepel, a geneticist at Cold Spring Harbor Laboratory on Long Island who was not involved in the new study, said the hypothesis fit the evidence. “I think that’s absolutely possible,” he said.

The new study raises a host of tantalizing implications about human history.

It is not possible to know just how many times these early Africans interbred with Neanderthals. But somewhere in prehistory, at least one female human from Africa must have carried the child of a male Neanderthal.

“Now you have this hybrid child, which is probably pretty unusual-looking,” Dr. Siepel said. “One way or another, this hybrid individual was absorbed into Neanderthal society.”

Dr. Siepel warned that the hypothesis hinges on the new DNA found in the Hohlenstein-Stadel fossil. Dr. Krause and his colleagues are now trying to retrieve nuclear DNA from the fossil.

The research at Sima de los Huesos shows just how far back in time scientists can now search for genes. The most revealing DNA might come from the mountains of Morocco.

There, scientists may be able to find genes from the earliest Homo sapiens, which they can then compare to Neanderthals’.

“These are things that I never thought possible five years ago,” Dr. Krause said.

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