Humans' hunter-gatherer ancestors were long-distance endurance athletes

London, June 6 (ANI): A new study has claimed that humans are hardwired to be endurance athletes - explaining why we get a 'runners' high' after exercise.

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- according to the study published in the Journal of Experimental Biology.

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

"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," the Daily Mail quoted Professor David Raichlen, from the University of Arizona, USA, as saying.

"We got interested in the brain as a way to look at whether evolution generated exercise behaviours in humans through motivation pathways," he stated.

But as little was known about the role of endocanabinnoids in the other aerobically active mammals the team tested if running - and its feel-good effect - was hardwired in more active animals.

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.

"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,"said Professor Raichlen. (ANI)