Wednesday, February 12, 2014

Persistance Hunting forces us to reexamine our history and physiology

Running is one of our favorite pass times. There are dozens of magazines, websites and books dedicated to the subject. Yet is seems that modern society has barely scratched the surface of the human animal's running ability. 

In the 1990s an evolutionary biologist , Dennis Bramble, from the University of Utah, began wondering about the theories of his former grad student David Carrier. David Carrier was the first person to publish a connection between evolution, our unique human physiology and running. Carrier's theory was that our ancestors, the semisimian Australopithecus, became bipedal not to free their hands to carry weapons or to carry supplies but to open their lungs in order to breathe so they could run better. 

Bramble, being a runner, wanted to see if Carrier's theory meant that humans shared unique attributes with running mammals, like cheetahs, rather than with walkers, like chimps. As part of his research, he visited Harvard evolutionary anthropologist Dan Lieberman, who was in the midst of studying animals that run poorly. 

Bramble and Lieberman discovered that pigs and other nonrunning mammals lack what humans, horses and dogs have in their necks: the nuchal ligament that stabilizes the cranium at high speeds. They reveled that the human body has 26 unique morphological in a 2004 paper, "Endurance Running and the Evolution of Homo,". "From head to toe in humans, it all just works," says Lieberman. "We evolved to run."

According to the 2004 study published in Nature, elite human sprinters can run 10.2 m/s for about 15 s.  That is about 37km/h.  The same 2004 study found that, horses and antelopes can sustain 15-20 m/s for minutes.  Traveling 54-72 km/h for minutes, not seconds. While we lack the ability to run at high velocities, we excel at running slowly for a long durations of time. We not only excel over long distance running, but we can out endure our competitors when the conditions are harsh; hot and dry.

One of the adaptations that gives us a significant advantage over other members of the animal kingdom is our ability to control our body temperature.  Humans sweat, which allows for heat dissipation via evapotranspiration.  We are also relatively hairless, which decreases heat retention. Bramble and Lieberman explain that we have an additional cooling mechanism built into the distribution of our blood vessels.  They note that an intricate cranial venous system supplies, “blood that has been cooled by sweating in the face and scalp to cool, via counter current heat exchange in the cavernous sinus, hot arterial blood in the internal carotid artery before it reaches the brain.”  In other words, we are adapted to cool down hot blood before it reaches our brain.  Our prey may have been fast, but without this adaptation they were not able to sustain their running as effectively as the human animal.

Another unique adaptation is found in our anatomy. While humans still share 95 percent or more of our DNA with chimps, only human legs and feet are loaded with springlike ligaments and tendons that are essential for running. Chimps don't have much of a gluteus maximus either. Humans however have a  robust behind and it is not only our biggest muscle, it's also primarily used for running, firing at the moment of foot impact as a counterbalance to the chest that prevents us from falling on our faces. This system gives us a relative stride length that's longer than a galloping horse's. Our narrow waist allows us to swing our arms and run in a straight line. Even our short toes are perfect for running. 

Christopher McDougall wrote about this study in his best-selling book "Born to Run", challenging nearly everything we know about movement and the human body. "It's fascinating the way this is all connected," says Louis Liebenberg, one of the leading experts on persistence hunting. "By exploring our past, we are rediscovering new limits to our endurance that we were never fully aware of."

Louis Liebenberg a South African scientist studied persistence hunting firsthand for 25 years in the Kalahari. On one hunt in the late 1990s, Liebenberg saw men who ran down a kudu in three hours 35 minutes and traveling at 35km. As the hunt progressed, the trackers seemed to enter what the scientist calls a "trancelike state." The experience left Liebenberg certain that "the full picture of why we became human must include running, it absolutely must."

Liebenberg says, "When you take all this data in with an open mind, there's just no other explanation: We evolved as runners." Watching the predatory runners of the Xo San tribe in action makes for a moot debate about the existence and effectiveness of persistence hunting. The running men keep their pace effortlessly for hours, across one of the harshest climates on earth. When they see erratic tracks in the sand indicating that the kudu is tiring, they know the kudu's time is drawing to an end. They call themselves "sons of the first people". 

The hunt ends (and is included in the clip below) when Karoha walks up to the animal and plunges a wood spear into its chest. The act that is largely ceremonial as the kudu has already collapsed from exhaustion.  Karoha then kneels and quietly honors the kudu by ritualistically spreading sand over its body, placing a left in its mouth and transferring saliva from the antelope's mouth onto his legs. The reverence and respect Karoha shows the kudu for giving his life is humbling. The kudu's graphic death was feared would be a disturbing part of the documentary, yet it turned out to be touching moment. At the movie's debut, the scene with Karoha and the kudu left many audience members in tears. Foster believes that witnessing a persistence hunt evokes an undeniable connection to our primal, predatory running past. "People were overcome," he says, "because they were seeing a deep, important part of themselves that they never knew existed."

Persistence Hunting Africa - Clip

This is a clip about persistence hunting in Africa. This refers back to barefoot running info. that we covered a few weeks ago. Persistence hunting has far reaching implications to human evolution, the role of females as active hunters and the results of the sedentary lifestyle of modern man.
*Warning, an animal will die in this clip, but I find the respect this man has for this animal is inspiring. 

Wishing you health and harmony today and everyday. Thank you for visiting.

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Bramble, D.M., Lieberman, D.E. 2004.  Endurance running and the evolution of Homo. Nature. 423:345-352
Liebenberg, L. 2008. The relevance of persistence hunting to human evolution. Journal of Human Evolution 55:1156–1159 


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