Saturday, June 9, 2012

Humans Evolved to be Persistence Hunters

I don't know if it is a well known fact, but it is a documented fact that several North American Indian tribes have engaged in persistence hunting--literally running deer to the ground based on the superior endurance of a human in running long distances. As an example, here is an article in a 1978 Sports Illustrated, and a more recent one on the practice from Outside magazine. It is also mentioned in this brief history of the Seri Indians of Sonora, Mexico.

With this background, I would direct your attention to this article from the Daily Mail from a few days ago:
Humans are hardwired to be endurance athletes - explaining why we get a 'runners' high' after exercise, a study claims.

The 'runner's high' - which triggers the brain's pleasure circuits in the same way as some drugs - evolved as an evolutionary 'carrot' to keep us moving.

Our hunter-gatherer ancestors would have been the equivalent of today's long-distance endurance athletes - and the key to humans evolving this skill was the 'high' we got from running.

A study compared humans and another animal that evolved to run - our best friend, the dog - with lazier animals, ferrets.

Ferrets seem to feel less reward from running - and in the wild, the animals don't race along like human beings or other athletic animals such as dogs.

Although we have become more sedentary in the last century these were not the conditions we evolved under, say researchers.

Our hunter-gatherer ancestors were long-distance endurance athletes and may have evolved that way because of the high that is experienced at the end of a run, it is claimed in the Journal of Experimental Biology. Professor David Raichlen, from the University of Arizona, USA, said: ‘Aerobic activity has played a role in the evolution of lots of different systems in the human body, which may explain why aerobic exercise seems to be so good for us.

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They set up an experiment with two species of natural athletes - humans and dogs - and a lazier animal, the ferret.

They found that animals that evolved for endurance exercise benefit from endocanabinoids while animals that did not don't experience the pleasures, leading them to propose that natural selection used the endocanabinoid system to motivate endurance exercise in humans.

The team trained participants to run and walk on a treadmill and collected blood samples from the participants before and after the exercise.

They analysed the endocanabinoid levels in the blood samples and found that the concentration of one endocanabinoid - anandamide - rocketed in the blood of the dogs and humans after a brisk run.

They also tested the human runners' state of mind and found that they athletes were much happier after the exercise.

However, when the team analysed the ferrets' blood samples, the animal's anandamide levels did not increase during exercise. They did not produce endocanabinoids in response to high-intensity exercise.

Professor Raichlen said: ‘These results suggest that natural selection may have been motivating higher rather than low-intensity activities in groups of mammals that evolved to engage in these types of aerobic activities.’

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