NPR science reporter Christopher Joyce this month profiled the research of University of Arizona anthropologist David Raichlen and his hypothesis that humans are, basically, adapted to run. Well, they are not so much as adapted, but literally “wired to run.”

Raichlen’s lab’s research focusses on: evolutionary biomechanics, linking physical activity to physiology and neurobiology in humans and other critters, and studying energetics and activity levels in human hunter-gatherers and other critters. Raichlen’s team is trying to link these elements to paint a picture of how aerobic activity levels impacted our evolution.

The story quotes Raichlen, who says: “Wired to run, meaning that our brains are probably, have been sort of rewired from an evolutionary sense to encourage these running and high aerobic-activity behaviors.” The theory by some anthropologists assumes that early humans learned to run long distances in order to chase down and exhaust prey, like antelopes. The evolutionary payoff for this difficult activity would be survival in the form of all kinds of goodies – nutritious and healthy food, particularly protein, not to mention clothing and bones for tools.

However, Raichlen believes there was another reward: the so-called “runner’s high.” This high is the release of naturally produced body chemicals cannabinoids, similar to the chemicals in marijuana.

I find this term misused and applied to different sensations, which some say is “euphoria,” but I mainly link to the relaxed feeling that follows runs. As a lifelong runner, I can personally testify to what I believe to be the “runner’s high,” and the sensation running provides to my mental mood, overall body feeling, and attitude. And the absence of running, in my case and in those of my many running friends, definitely induces withdrawal symptoms, irritability, and poor moods and worse performance in other activities.

Raichlen and his researchers designed a test to determine if other distance-running mammals also produced those drugs. He did that by putting ferrets and dogs on treadmills and taking samples of their blood. Turns out that dogs, who are also are built for distance, produced the drug and the ferrets did not (ferrets are not built for distance).

The team’s paper was published in the Journal of Experimental Biology in December 2011, which of course is locked behind a firewall that the general public cannot access without paying a hefty fee, a frustrating feature of the marketplace of publicly-funded science and the monopolies that control the publication of peer-reviewed journals (but I digress).

I also find it, again, interesting how dogs and humans share this trait and seem amazingly co-adapted to share this wonderful activity of running. I personally have never been able to tell if humans or canines enjoy running more than the other. I just know that humans and dogs usually have that same wonderful expression of contentment when they finish their outings. It is the look of bliss, and if Raichlen is right, it is an evolutionary advantage.