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.
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 the size that 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 B, 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.
Harold Gage slowly backs his semitrailer up next to the fence at his Rozet home. His friend Tyler Hippen trails behind, making fresh footprints in the snow. As the sun sinks, the temperature falls steadily toward zero. Gage's girlfriend Lisa Winjum runs inside the house to put on warmer clothes, but she's right back outside as soon as her coveralls are buckled.
Gage steps down from the cab, and he, Winjum, Hippen and two others get to work loosening the tight straps that hold 13 round bails of hay to the trailer. One by one, they pull the straps off and stow them under the cab.
Gage and Hippen then hoist the skinnier of the other two men up onto the truck. He leans back on one of the round bales and gets ready to push with his legs. Winjum calls her dogs away from the truck, and on the count of three the men kick and push the first hay bale off the rig. Once one falls off, the rest is easy.
They all jump up on the trailer, and after a few minutes of grunting and shoving, the remainder of the load is off. The round bales weigh between 1,700 and 1,800 pounds. They fall to the ground with a thud, and they don't bounce. These bales are solid, fresh hay wrapped up tight, with no mold in the middle.
With such a bad drought this season, seeing more than a few bales of hay spread out on one property is uncommon in Campbell County. Hay is so tough to come by that many ranchers have had to downsize their cattle herds, selling cows and giving away horses that they cannot afford to feed.
But Gage and Winjum have worked out a system. Three or four times a week, the couple or a hired driver travel 430 miles up to Wildrose, N.D., to pick up 26 bales of hay, a full truckload on Gage's semi. Once they get the hay loaded and securely strapped down — at least a two-hour process — the pair turn around and drive the 430 miles back.
While the two own 26 horses, they don't need that much hay for themselves. They know the livestock community is hurting, so they sell what they can at a fair price — $165 per bale, to be exact.
Winjum said some hay in the area is going for $250 to $300 per ton, up from the typical price of around $100 per ton last year. She said they'd sell their bales for less, but they need to take transportation costs into consideration.
"We figured out how much it would cost to get Harold's semi up and running again, and licensing, permits in each state, insurance, tires, fuel, truck driver pay and maintenance," Winjum said.
As soon as she posted an ad on Craigslist around Thanksgiving, they started getting calls. The couple deliver to a few regular customers, but they hear from someone new almost every day.
"It seems like most of the people are new people," Gage said. "They're just in dire need of hay, and they need it now."
Janet and Bill Woodworth are regular customers who heard about Gage and Winjum through word of mouth. Janet Woodworth has been raising cows all her life.
"We've always had hay, and we've always been able to have some carry-over hay," Woodworth said. "There was only one year we had to buy a little bit, and that was probably 15 years ago."
Not only has Woodworth had to buy numerous bales of hay this year, she has already had to sell six cows to be able to afford to feed the rest.
"It's a sad year," Woodworth said. "All this beautiful weather this fall and winter is not good for us. It's getting scary for next year."
This is the first year Gage and Winjum have done something so drastic to be able to feed their animals, but they may have to keep it up if Wyoming doesn't get more precipitation.
The couple aren't making much money delivering the hay. In fact, they're barely breaking even. But the animal lovers are in it for the livestock and for the families whose livelihoods depend on them.
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