Hispanic Pregnancies Fall in U.S. as Women Choose Smaller Families

ORLANDO, Fla. — Hispanic women in the United States, who have generally had the highest fertility rates in the country, are choosing to have fewer children. Both immigrant and native-born Latinas had steeper birthrate declines from 2007 to 2010 than other groups, including non-Hispanic whites, blacks and Asians, a drop some demographers and sociologists attribute to changes in the views of many Hispanic women about motherhood.

As a result, in 2011, the American birthrate hit a record low, with 63 births per 1,000 women ages 15 to 44, led by the decline in births to immigrant women. The national birthrate is now about half what it was during the baby boom years, when it peaked in 1957 at 122.7 births per 1,000 women of childbearing age.

The decline in birthrates was steepest among Mexican-American women and women who immigrated from Mexico, at 25.7 percent. This has reversed a trend in which immigrant mothers accounted for a rising share of births in the United States, according to a recent report by the Pew Research Center. In 2010, birthrates among all Hispanics reached their lowest level in 20 years, the center found.

The sudden drop-off, which coincided with the onset of the recession, suggests that attitudes have changed since the days when older generations of Latinos prized large families and more closely followed Roman Catholic teachings, which forbid artificial contraception.

Interviews with young Latinas, as well as reproductive health experts, show that the reasons for deciding to have fewer children are many, involving greater access to information about contraceptives and women’s health, as well as higher education.

When Marucci Guzman decided to marry Tom Beard here seven years ago, the idea of having a large family — a Guzman tradition back in Puerto Rico — was out of the question.

“We thought one, maybe two,” said Ms. Guzman Beard, who gave birth to a daughter, Attalai, four years ago.

Asked whether Attalai might ever get her wish for a little brother or sister, Ms. Guzman Beard, 29, a vice president at a public service organization, said: “I want to go to law school. I’m married. I work. When do I have time?”

The decisions were not made in a vacuum but amid a sputtering economy, which, interviewees said, weighed heavily on their minds.

Latinos suffered larger percentage declines in household wealth than white, black or Asian households from 2005 to 2009, and, according to the Pew report, their rates of poverty and unemployment also grew more sharply after the recession began.

Prolonged recessions do produce dips in the birthrate, but a drop as large as Latinos have experienced is atypical, said William H. Frey, a sociologist and demographer at the Brookings Institution. “It is surprising,” Mr. Frey said. “When you hear about a decrease in the birthrate, you don’t expect Latinos to be at the forefront of the trend.”

D’Vera Cohn, a senior writer at the Pew Research Center and an author of the report, said that in past recessions, when overall fertility dipped, “it bounced back over time when the economy got better.”

“If history repeats itself, that will happen again,” she said.

But to Mr. Frey, the decrease has signaled much about the aspirations of young Latinos to become full and permanent members of the upwardly mobile middle class, despite the challenges posed by the struggling economy.

Jersey Garcia, a 37-year-old public health worker in Miami, is in the first generation of her family to live permanently outside of the Dominican Republic, where her maternal and paternal grandmothers had a total of 27 children.

“I have two right now,” Ms. Garcia said. “It’s just a good number that I can handle.”

“Before, I probably would have been pressured to have more,” she added. “I think living in the United States, I don’t have family members close by to help me, and it takes a village to raise a child. So the feeling is, keep what you have right now.”

But that has not been easy. Even with health insurance, Ms. Garcia’s preferred method of long-term birth control, an IUD, has been unaffordable. Birth control pills, too, with a $50 co-payment a month, were too costly for her budget. “I couldn’t afford it,” she said. “So what I’ve been doing is condoms.”

According to research by the National Latina Institute for Reproductive Health, the overwhelming majority of Latinas have used contraception at some point in their lives, but they face economic barriers to consistent use. As a consequence, Latinas still experience unintended pregnancy at a rate higher than non-Hispanic whites, according to the institute.

And while the share of births to teenage mothers has dropped over the past two decades for all women, the highest share of births to teenage mothers is among native-born Hispanics.

“There are still a lot of barriers to information and access to contraception that exist,” said Jessica Gonzáles-Rojas, 36, the executive director of the institute, who has one son. “We still need to do a lot of work.”

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House Takes On Fiscal Cliff

Molly Riley/Agence France-Presse — Getty Images

Representative Eric Cantor arrived at the Capitol on Tuesday.

WASHINGTON — House Republicans reacted with anger Tuesday afternoon to a Senate-passed plan to head off automatic tax increases and spending cuts, putting the fate of the legislation in doubt just hours after it appeared Congress was nearing a resolution of the fiscal crisis.

Lawmakers said that Representative Eric Cantor of Virginia, the No. 2 Republican, indicated to his colleagues in a closed-door meeting in the basement of the Capitol that he could not support the legislation in its current form. Many other Republicans were voicing stiff objections to a plan that they saw as raising taxes while doing little to rein in spending. Several conservatives assailed it on the House floor as the chamber convened at noon for an unusual New Year’s Day session.

The aides said that Speaker John A. Boehner, who had pledged to put any measure the Senate passed on the House floor for a vote, was mainly listening to the complaints of his rank and file and had not taken a firm position on the legislation, though he had clear reservations.

The situation loomed as a significant test for Mr. Boehner, who had been unable to pass his own proposal to increase taxes only on $1 million in income and above. He has said repeatedly that he would allow a vote on the Senate bill, but he has also said he did not want to pass a bill with predominantly Democratic votes. Public opposition from Mr. Cantor, who has up to this point sided with Mr. Boehner in the fiscal fight, would also complicate his position.

After taking the pulse of its membership, the Republican leadership was expected to try to determine how to proceed on the legislation with the 112th Congress about to come to a close Thursday.

Democrats emerged from their own closed-door meeting with Vice President Joseph R. Biden Jr. generally sanguine about the deal, if not ecstatic. Few Democrats, if any, suggested a Democratic rebellion was in the works after a forceful — and lengthy — presentation by Mr. Biden, which walked them step by step through the negotiations, the legislation and the path forward on future deficit confrontations.

“It is clear that the vice president and the president are convinced that they have done the right thing. They don’t see it as a perfect deal though, and nobody else does,” said Representative Elijah Cummings, Democrat of Maryland.

It appeared that members were favoring trying to amend the measure and send it back to the Senate.

“I would be shocked if this bill doesn’t go back to the Senate,” said Representative Spencer Bachus, Republican of Alabama.

With just two days to go before a new Congress convenes, the House has essentially three choices: reject the bill, pass it as written by the Senate after what is certain to be a robust, even rancorous debate, or amend the bill and quickly return it across the rotunda to the Senate. Should the House choose to amend the measure, it would almost certainly imperil its chances of becoming law before the new Congress convenes. The Senate compromise, which enjoyed wide bipartisan support, was so hard fought and senators do not anticipate taking another vote on it.

Any failure to pass the measure before the 112th Congress ends as of noon Thursday would require the process to start over in the new 113th Congress, meaning the Senate would have to vote again with a changed membership due the departure of several veteran lawmakers and the arrival of newcomers from both parties as a result of victories in the November elections.

But the strong, bipartisan 89-to-8 vote in the Senate about 2 a.m. on Tuesday will put strong pressure on the House to approve the legislation since a defeat would essentially leave the House responsible for a steep series of tax increases and spending cuts that some economists warn could send the nation back into a recession.

Yet it was clear Tuesday morning that many House Republicans were disenchanted with the plan, which, while containing many concessions that angered Democrats, still favors the latter party’s priorities and imposes a tax increase on the wealthiest Americans.

“I am halfway through reading it and haven’t found the cuts yet,” said Representative Trey Gowdy of South Carolina, who generally votes against budget bills. “It’s part medicinal, part panacea, and part treating the symptoms but not the underlying pathology.”

Democrats have their own issues with the measure because of what they see as too many concessions on taxes, making it apparent some combination of Democrats and Republicans will have to come together behind the measure if it is to clear the House and be sent to President Obama for his signature.

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Obama urges Congress to reach a 'fiscal cliff' deal

President Obama says it appears that an agreement to avoid the fiscal cliff is 'in sight,' but says it's not yet complete and work continues.

WASHINGTON – As negotiators closed in on a tax-and-spending deal to avert the “fiscal cliff,”  President Obama delivered a nationally televised plea Monday for a final push by Congress in the hours remaining before midnight Monday when taxes are set to increase.

“They’re close, but they’re not there yet,” Obama said, referring to bipartisan talks led by Vice President Joe Biden and Senate Republican leader Mitch McConnell of Kentucky.

The president added, “if there’s one second left” before Congress has to act, “they will use that last second.” Among the issues left to be resolved, he said, confirming earlier news reports, is an agreement that would delay across-the-board spending cuts, which would otherwise go into effect on Wednesday.

“So keep the pressure on over the next 12 hours or so,” he said to an invited audience that reacted with applause and laughter to his brief remarks, including when he said that he would be spending New Year’s Eve in Washington as lawmakers try to finalize a deal that can win approval in both houses.

QUIZ: How much do you know about the fiscal cliff?

Obama appeared to anticipate criticism, already building from liberals, that he is giving too much away.  He won re-election last month on a plan to raise taxes on annual income above $250,000 for couples. But the deal would raise that threshold to $450,000 a year, and generate considerably less than half of the $1.6 trillion in additional revenue over 10 years that Obama had initially sought.

The president emphasized that the potential agreement, though “modest,” would achieve his “top priority:” preventing an income tax hike on 98% of U.S. taxpayers.

He also pointed out that the deal would extend tax credits for families with children, tuition tax credits for college students, tax credits for clean energy and extended unemployment benefits for 2 million jobless Americans.

Obama said he would have preferred a much larger agreement on government revenues and long-term spending. “But with this Congress, that was obviously a little too much to hope for,” he said, to laughter from the audience.

And while he insisted that Congress needed to stay focused on the needs of the American people – “not politics” – he drew applause when he boasted that the potential deal, if approved, would result in something that Republicans had said they “would never agree” to: a permanent tax-rate increase on the wealthiest Americans.

PHOTOS: President Obama’s past

He also began staking out political turf for the next phase of the tax-and-spending fight, which will play out over much of 2013, if not longer. Any agreement to deal with spending cuts would have to be balanced, with increased revenues as one part of the equation.

If Republicans think that can “shove only spending cuts” as a way of shrinking the deficit in future years, “they have another think coming. That’s not how it’s going to work,” Obama said.

However, some liberals, including former Obama administration economic advisor Jared Bernstein, are warning that Republicans will never agree to higher taxes beyond those contained in whatever year-end deal is finally struck.

The highly choreographed event at the White House office complex included what Obama aides described as middle-class taxpayers. Obama shook hands with many of the 14 men and women who stood onstage behind him, then ushered them into another room for a photo session.

Obama ended what may have been his final public event of 2012 by wishing everyone a happy new year.

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The Best of Exploration: Top 8 Stories of Space Exploration in 2012

Our recap of the year’s best exploratory exploits continues today with a look at the biggest developments in space exploration. 2012 saw the stunning debut of new spacecraft (Curiosity), the continued contributions of geriatric ones (Voyager), and the first full year since the end of the Space Shuttle program. Casey Dreier of The Planetary Society nominated 8 particularly meaningful developments from the last twelve months.

Image: Dreier’s pick for image of the year, a Cassini photograph of Saturn’s north pole through an infrared filter. (Credit: NASA / JPL / SSI / Emily Lakdawalla)

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Armstrong better, Green Day to resume tour in 2013

LOS ANGELES (AP) — Green Day is going back out on the road.

The Grammy-winning punk band announced new tour dates Monday.

The band canceled the rest of its 2012 club schedule and postponed the start of a 2013 arena tour after singer-guitarist Billie Joe Armstrong‘s substance abuse problems emerged publicly in September when he had a profane meltdown on the stage of the iHeartRadio Music Festival in Las Vegas.

Armstrong told fans in a statement Monday that he’s “getting better every day” and “the show must go on.”

The tour is scheduled to begin March 28 at the Allstate Arena in the Chicago area.

The band released its most recent album, “Tre,” on Dec. 11, more than a month ahead of schedule.

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Personal Health: Food Myths

Let’s start the new year on scientifically sound footing by addressing some nutritional falsehoods that circulate widely in cyberspace, locker rooms, supermarkets and health food stores. As a result, millions of people are squandering hard-earned dollars on questionable, even hazardous foods and supplements.

For starters, when did “chemical” become a dirty word? That’s a question raised by one of Canada’s brightest scientific minds: Joe Schwarcz, director of the Office for Science and Society at McGill University in Montreal. Dr. Schwarcz, who has received high honors from Canadian and American scientific societies, is the author of several best-selling books that attempt to set the record straight on a host of issues that commonly concern health-conscious people.

I’ve read two of his books, “Science, Sense and Nonsense” (published in 2009) and “The Right Chemistry” (2012), and recently attended a symposium on the science of food that Dr. Schwarcz organized at McGill.

What follows are tips from his books and the symposium that can help you make wiser choices about what does, and does not, pass your lips in 2013.

CURED MEATS Many health-conscious people avoid cured meats like hot dogs and bacon because the nitrites with which they are preserved can react with naturally occurring amines to form nitrosamines. Nitrosamines have produced mutations in cells cultured in the laboratory and cancer in animals treated with very high doses.

As an alternative, sandwich lovers often buy organic versions of processed meats or products without added nitrites. Without preservatives, these foods may not be protected from bacterial contamination. And despite their labels, they may contain nitrites. According to Dr. Schwarcz, organic processed meats labeled “uncured” may be preserved with highly concentrated, nitrate-rich celery juice treated with a bacterial culture that produces nitrites.

If you’re really concerned about your health, you’d be wise to steer clear of processed meats — organic, nitrite-free or otherwise. High saturated fat and salt content place them low on the nutritional totem pole.

MEAT GLUE Never heard of it? You may have eaten it, especially if you dine out often. At WD-50 in New York, the chef, Wylie Dufresne, makes his famous shrimp noodles with the enzyme transglutaminase, a k a meat glue. It binds protein molecules, gluing together small pieces of fish, meat or poultry.

The Japanese use meat glue to create artificial crab meat from pollock. Others use it to combine lamb and scallops, or to make sausages that hold together without casings.

Sound frightening? It shouldn’t. The enzyme is classified by the Food and Drug Administration as “generally recognized as safe,” and there is no reason to think otherwise. Our bodies produce it to help blood clot, Dr. Schwarcz points out. When consumed, it breaks down like any protein into its component amino acids in our digestive tracts.

There is, however, one possible indirect hazard: If glued-together animal protein is not thoroughly cooked, dangerous bacteria that originally contaminated the meat could remain viable within the fused product.

TRANS FATS The removal of heart-damaging trans fats from processed foods is a much-ballyhooed boon to health. But “not all trans fats are fiends,” Dr. Schwarcz notes. Certain ones can legally, and healthfully, be added to dairy products, meal-replacement bars, soy milk and fruit juice.

The word “trans” refers to the arrangement of hydrogen and carbon atoms in a fatty acid. The trans formation linked to heart disease is formed when vegetable oils are hardened to prolong shelf life in a manufacturing process called hydrogenation. Natural trans fats, like those in meat and dairy products, take a slightly different form, resulting in an entirely different effect on health.

The most widely consumed “good” trans fat is conjugated linoleic acid, which research has shown can help weight-conscious people lose fat and gain muscle. Various studies have suggested that C.L.A., now widely sold as a supplement, also can enhance immune function and reduce atherosclerosis, high blood pressure and inflammation.

ORGANIC OR NOT? Wherever I shop for food these days, I find an ever-widening array of food products labeled “organic” and “natural.” But are consumers getting the health benefits they pay a premium for?

Until the 20th century, Dr. Schwarcz wrote, all farming was “organic,” with manure and compost used as fertilizer and “natural” compounds of arsenic, mercury and lead used as pesticides.

Might manure used today on organic farms contain disease-causing micro-organisms? Might organic produce unprotected by insecticides harbor cancer-causing molds? It’s a possibility, Dr. Schwarcz said. But consumers aren’t looking beyond the organic sales pitch.

Also questionable is whether organic foods, which are certainly kinder to the environment, are more nutritious. Though some may contain slightly higher levels of essential micronutrients, like vitamin C, the difference between them and conventionally grown crops may depend more on where they are produced than how.

A further concern: Organic producers disavow genetic modification, which can be used to improve a crop’s nutritional content, enhance resistance to pests and diminish its need for water. A genetically modified tomato developed at the University of Exeter, for example, contains nearly 80 times the antioxidants of conventional tomatoes. Healthier, yes — but it can’t be called organic.

FARMED SALMON Most of the salmon consumed nowadays is farmed. Even if we all could afford the wild variety, there’s simply not enough of it to satisfy the current demand for this heart-healthy fish.

There may be legitimate concerns about possible pollutants in farmed salmon, but one concern that is a nonissue involves that “salmon” color, produced by adding astaxanthin to fish feed. This commercially made pigment is an antioxidant found naturally in algae, and it is carried up the food chain to give wild salmon its color, too.

NUTS Growing up, I was often warned to avoid nuts because they’re “fattening.” Now I know better. Research has shown that people who regularly eat nuts and nut butters in normal amounts weigh less, on average, than nut avoiders.

The fat in nuts is unsaturated and heart-healthy. Nuts are also good sources of protein, antioxidants, vitamins, minerals and fiber, and can help keep between-meal hunger at bay. The same is true of avocados — just don’t go overboard.

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Boehner: Obama won't stand up to his own party on 'fiscal cliff'

WASHINGTON -- House Speaker John A. Boehner called it “ironic” that President Obama blamed Republicans for stalled negotiations on the "fiscal cliff" and accused the Democrat of being unwilling to stand up to his own party.

Responding to Obama’s appearance on NBC’s “Meet The Press,” the Ohio Republican said the GOP has been “reasonable and responsible” throughout the talks.

“In an effort to get the president to agree to cut spending -- which is the problem -- I put revenues on the table last year, and I put them on the table again last month,” Boehner said in a statement. “Republicans made every effort to reach the ‘balanced’ deficit agreement that the president promised the American people, while the president has continued to insist on a package skewed dramatically in favor of higher taxes that would destroy jobs.”

In an interview taped Saturday, Obama told NBC’s David Gregory that he remained “optimistic” that a deal could be reached, but said that in his mind, the sticking point was that Republicans “have had trouble saying yes to a number of repeated offers.”

QUIZ: How much do you know about the fiscal cliff?

“Congress has not been able to get this stuff done, not because Democrats in Congress don't want to go ahead and cooperate, but because I think it's been very hard for Speaker Boehner and Republican Leader [Mitch] McConnell to accept the fact that taxes on the wealthiest Americans should go up a little bit, as part of an overall deficit reduction package,” he said.

“I negotiated with Speaker Boehner in good faith and moved more than halfway in order to achieve a grand bargain.”

Earlier this month, Obama had offered to raise the income threshold for higher tax rates to $400,000, from the $250,000 he had campaigned on. Boehner pulled back from the negotiations and tried to pass what he called "Plan B," which would have boosted the threshold to $1 million. He failed to get support from House Republicans and did not bring it to the floor.

Don Stewart, a spokesman for Senate Republican Leader Mitch McConnell, responded that “while the president was taping those discordant remarks yesterday, Sen. McConnell was in the office working to bring Republicans and Democrats together on a solution. Discussions continue today.”

In his statement, Boehner noted that the House has passed multiple bills that would avert the entire fiscal cliff, addressing both the looming across-the-board tax increases and deep spending cuts.

“The president has never called for the Senate to act on those bills in any way. He instead has simply allowed the Democratic-controlled Senate to sit on them and lead our economy to the edge of the fiscal cliff,” Boehner said.

PHOTOS: Notable moments of the 2012 presidential election

The Senate has passed budget bills that the House has not acted upon.

The House is due to gavel in Sunday afternoon, with votes expected on unrelated bills. The Senate is in session while leaders and staff continue to seek a solution that would garner enough votes to move over to the House.

“We know that there are negotiations going on,” Sen. Barbara Boxer (D-Calif.) said on the Senate floor. “I really hope our leaders can find a way out of this.”

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Wired Science's Top Image Galleries of the Year

Many of our most popular posts are image galleries, and this year our readers favorite collections included microscope photos, doomsday scenarios, auroras and lots of images of Earth from space.

The satellite image above of Brasilia is part of the most popular post of the year.

Above:

I think it's safe to say that our readers like looking at images of Earth from space almost as much as we do. Satellite imagery was the subject of four of Wired Science's 10 most popular galleries of 2012, with this gallery of planned cities topping the list.

See the full gallery.

Image: NASA/USGS

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‘The Hobbit’ stays atop box office for third week

LOS ANGELES (AP) — “The Hobbit: An Unexpected Journey” continues to rule them all at the box office, staying on top for a third-straight week with nearly $ 33 million.

The Warner Bros. fantasy epic from director Peter Jackson, based on the J.R.R. Tolkien novel, has made $ 222.7 million domestically alone.

Two big holiday movies — and potential awards contenders — also had strong openings. Quentin Tarantino‘s spaghetti Western-blaxploitation mash-up “Django Unchained” came in second place for the weekend with $ 30.7 million. The Weinstein Co. revenge epic, starring Jamie Foxx and Christoph Waltz, has earned $ 64 million since its Christmas Day opening.

And in third place with $ 28 million was the sweeping, all-singing “Les Miserables.” The Universal Pictures musical starring Hugh Jackman and Anne Hathaway has made $ 67.5 million since debuting on Christmas.

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Well: Exercise and the Ever-Smarter Human Brain

Anyone whose resolve to exercise in 2013 is a bit shaky might want to consider an emerging scientific view of human evolution. It suggests that we are clever today in part because a million years ago, we could outrun and outwalk most other mammals over long distances. Our brains were shaped and sharpened by movement, the idea goes, and we continue to require regular physical activity in order for our brains to function optimally.

Phys Ed

Gretchen Reynolds on the science of fitness.

The role of physical endurance in shaping humankind has intrigued anthropologists and gripped the popular imagination for some time. In 2004, the evolutionary biologists Daniel E. Lieberman of Harvard and Dennis M. Bramble of the University of Utah published a seminal article in the journal Nature titled “Endurance Running and the Evolution of Homo,” in which they posited that our bipedal ancestors survived by becoming endurance athletes, able to bring down swifter prey through sheer doggedness, jogging and plodding along behind them until the animals dropped.

Endurance produced meals, which provided energy for mating, which meant that adept early joggers passed along their genes. In this way, natural selection drove early humans to become even more athletic, Dr. Lieberman and other scientists have written, their bodies developing longer legs, shorter toes, less hair and complicated inner-ear mechanisms to maintain balance and stability during upright ambulation. Movement shaped the human body.

But simultaneously, in a development that until recently many scientists viewed as unrelated, humans were becoming smarter. Their brains were increasing rapidly in size.

Today, humans have a brain that is about three times larger than would be expected, anthropologists say, given our species’ body size in comparison with that of other mammals.

To explain those outsized brains, evolutionary scientists have pointed to such occurrences as meat eating and, perhaps most determinatively, our early ancestors’ need for social interaction. Early humans had to plan and execute hunts as a group, which required complicated thinking patterns and, it’s been thought, rewarded the social and brainy with evolutionary success. According to that hypothesis, the evolution of the brain was driven by the need to think.

But now some scientists are suggesting that physical activity also played a critical role in making our brains larger.

To reach that conclusion, anthropologists began by looking at existing data about brain size and endurance capacity in a variety of mammals, including dogs, guinea pigs, foxes, mice, wolves, rats, civet cats, antelope, mongooses, goats, sheep and elands. They found a notable pattern. Species like dogs and rats that had a high innate endurance capacity, which presumably had evolved over millenniums, also had large brain volumes relative to their body size.

The researchers also looked at recent experiments in which mice and rats were systematically bred to be marathon runners. Lab animals that willingly put in the most miles on running wheels were interbred, resulting in the creation of a line of lab animals that excelled at running.

Interestingly, after multiple generations, these animals began to develop innately high levels of substances that promote tissue growth and health, including a protein called brain-derived neurotrophic factor, or BDNF. These substances are important for endurance performance. They also are known to drive brain growth.

What all of this means, says David A. Raichlen, an anthropologist at the University of Arizona and an author of a new article about the evolution of human brains appearing in the January issue of Proceedings of the Royal Society Biology, is that physical activity may have helped to make early humans smarter.

“We think that what happened” in our early hunter-gatherer ancestors, he says, is that the more athletic and active survived and, as with the lab mice, passed along physiological characteristics that improved their endurance, including elevated levels of BDNF. Eventually, these early athletes had enough BDNF coursing through their bodies that some could migrate from the muscles to the brain, where it nudged the growth of brain tissue.

Those particular early humans then applied their growing ability to think and reason toward better tracking prey, becoming the best-fed and most successful from an evolutionary standpoint. Being in motion made them smarter, and being smarter now allowed them to move more efficiently.

And out of all of this came, eventually, an ability to understand higher math and invent iPads. But that was some time later.

The broad point of this new notion is that if physical activity helped to mold the structure of our brains, then it most likely remains essential to brain health today, says John D. Polk, an associate professor of anthropology at the University of Illinois at Urbana-Champaign, and co-author, with Dr. Raichlen, of the new article.

And there is scientific support for that idea. Recent studies have shown, he says, that “regular exercise, even walking,” leads to more robust mental abilities, “beginning in childhood and continuing into old age.”

Of course, the hypothesis that jogging after prey helped to drive human brain evolution is just a hypothesis, Dr. Raichlen says, and almost unprovable.

But it is compelling, says Harvard’s Dr. Lieberman, who has worked with the authors of the new article. “I fundamentally agree that there is a deep evolutionary basis for the relationship between a healthy body and a healthy mind,” he says, a relationship that makes the term “jogging your memory” more literal than most of us might have expected and provides a powerful incentive to be active in 2013.

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