April 25, 2011

HOW MUCH FOOD DO YOU SUPPOSE THEY RUN PAST IN THIS PURSUIT?:

Fair Chase: On the plains of New Mexico, a band of elite marathoners tests a controversial theory of evolution: that humans can outrun the fastest animals on earth. (Charles Bethea, May 2011, Outside)

AS RIDICULOUS AS THIS spectacle might appear, the men are testing a much-debated scientific notion about when and how ­humans became hunters. Between two and three million years ago, when our australo­pithecine ancestors ventured out of the forests and onto the protein-rich African savanna, they were prey more often than hunter. They gathered plant-based foods, just as their primate brethren did. Then something changed. They began running after game with long, steady strides. Evolutionary biologists like Harvard's Dan Lieberman think the uniquely human capacity for endurance running is a distant remnant of prehistoric persistence hunting.

We can run all day, the theory goes, because there was once a caloric advantage to it. Our two human legs, packed as they are with long slow-twitch muscle fibers, make us better runners over long distances than most quad­rupeds. And our three million sweat glands give us the ability to cool our bodies with perspiration. An antelope, by contrast, sprints—for up to 15 minutes—while wearing a fur coat and relies on respiration (panting) to release the heat that builds up with exertion. Add to the mix our ability to organize and strategize and, well, you can see how persistence hunting might actually work.

In Christopher McDougall's 2009 book Born to Run, a bestseller that examined the history and science of endurance running, Lieberman explained that a successful persistence hunt probably began with scaring the quarry into a long gallop on a hot day. "If you keep just close enough for it to see you, it will keep sprinting away," he said. "After about 10 or 15 kilometers' worth of running, it will go into hyperthermia and collapse."

Of course, "hot" means approaching 100 degrees Fahrenheit, and 10 to 15 kilometers is a low-end estimate. Biologist and ultramara­thoner Bernd Heinrich described it more succinctly in his 2001 book Why We Run: "The sprints cost them dearly in the end."

There's no hard archaeological evidence of persistence hunting, but half a dozen tribes are known to have pursued game this way in the past century: the Aborigines in Australia, the Navajo in the American Southwest, the Seri and Tarahumara Indians in Mexico. Of the tribes thought to practice it, though, only the Bushmen of the Kalahari Desert have been seen chasing antelope in recent decades. In the 1980s, South African mathematician Louis Liebenberg joined a successful Bushman persistence hunt for kudu in 107-degree heat. It nearly killed him, too.

The Santa Fe team figured that persistence hunting would work just as well on an American antelope, which may have been something of a blunder. Neither Lieberman nor McDougall nor Heinrich knows of anybody who's caught a pronghorn this way. The speed goat, as it's sometimes called, isn't technically an antelope at all but the lone species of the Antilocapra genus, which evolved to flee the now extinct North American cheetah. The pronghorn's top speed of 60 mph is faster than any African ungulate.

In addition to its swiftness, the pronghorn has lungs the size of water-cooler jugs and wide-set eyes as large as an elephant's. It's capable of 340-degree vision, with acuity comparable to a pair of ten-power binoculars.

Evolutionary biologist David Carrier and his brother, Scott, who wrote the 2001 memoir Running After Antelope, made the single recorded attempt to chase down a pronghorn. Scott, a recreational runner, characterized the elusiveness of the animal, which they pursued in Wyoming, like so: "They blend and flow and change positions. There are no individuals but this mass that moves across the desert like a pool of mercury on a glass table." The brothers failed. The antelope, Scott wrote, "used the terrain to ditch us."

Musuva and his gang are much quicker than the Carrier brothers: the fastest of them has run a 2:10 marathon (six minutes off the world record) and the slowest, Espo­sito, a respectable 2:45. Vegas probably wouldn't like their odds, but who knows? If you believe Lieberman, our mere existence is a testament to our ancestors' success at this tiring pursuit.


Posted by at April 25, 2011 5:58 AM
  

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