Homo Sapiens Are “Wired to Run” by O’S News Service Running and Other Forms of Aerobic Ac- Damide Levels at All

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—10— O’Shaughnessy’s • Winter/Spring 2013 BeyondTHC.com Homo sapiens are “wired to run” By O’S News Service Running and other forms of aerobic ac- damide levels at all. such as an intestinal worm that had done tivity increase production of anandamide “This study provides the first evidence it harm. The precedent involved prong- —the neurotransmitter that THC imi- that inter-specific variation in neurotrans- horn… small, goat-sized animals. Though tates— in the brains of certain mammals, mitter signaling may explain differences in they are sometimes called antelope, they including people. The authors of a study locomotor behavior among mammals,” the are not precisely antelope and not pre- published this spring in the Journal Of Ex- authors conclude. “Thus, a neurobiological cisely deer either. They are unique. Their perimental Biology suggest that the brain’s reward for endurance exercise may explain branch on the tree of life has been separate reward system provided a neurobiological why humans and other cursorial mammals from other branches for much longer than incentive for our remote ancestors to run habitually engage in aerobic exercise de- humans have been separate from other pri- for long distances. The incentive promoted spite the higher associated energy costs and mates.” survival and thus helped shape the evolu- injury risks, and why non-cursorial mam- There are some 10 million pronghorn The ferret is a non-cursorial animal that tion of the human body. mals avoid such locomotor behaviors.” left on the western grasslands of North sleeps 14-18 hours and is active at dawn and The authors note that the same system America. “Once there were many kinds dusk. Ferrets were domesticated to hunt rab- “Cursorial” refers to animals that might have motivated distance running of’ pronghorn but now there is just a single bits. that run long distances —wolves, would also mitigate the pain and damage lithe species,” Dunn recounts. “The prong- horses, pronghorn, etc. involved. Anthropologists have long won- horn’s body is tan on the back and white “The pronghorn once had something to dered, Gerdeman adds in an email, “why on the belly. It has a dark black nose and flee. American cheetahs evolved to be fast- early hominids, for whom running would dark black two-pronged antlers. Compared er to pursue faster pronghorn and prong- The JEB paper by David Raichlen of have been much more difficult based on to elk, to moose, or even to true antelope, horn evolved to be even faster in return. the University of Arizona, Gregory Ger- their skeletal anatomy, would have en- pronghorns are dervishes —light and mus- Then humans arrived in the Americas and, demann of Eckerd College, and colleagues gaged in behaviors that are energetically cular. A pronghorn can run a hundred kilo- one way or another, killed off sixty large is called “Wired to run: exercise-induced taxing and increase the chance of injury meters an hour… Even after running fast mammal species, including the cheetah, endocannabinoid signaling in humans and in a predator-rich world?” He proposes and long, they can run faster and longer.” but also lions, mammoths, mastodons, and cursorial mammals with implications for an answer: “The endocannabinoid system “As recently as 10,000 years ago, just even camels. The extinction of these great as an engine driving evolutionary change. as cows were beginning to be domesticated beasts and, in particular, of the American Analgesia, anti-inflammatory, enhancing in Asia, the pronghorn lived on the plains cheetah, left the pronghorn anachronisti- bone density —it all fits this model.” with the gray wolf, black bear, grizzly cally and irrelevantly fast.” bear, and coyote, but also with other large The pronghorn had evolved to flee pred- Add to the Glossary: “Cursorial” predators. When humans first arrived in the ators —even the shape of the uterus has The word “cursorial” is related to Americas, they found the pronghorn and been designed for slenderness. But now “course,” meaning as a verb, “to run alongside them a much greater variety of that the predators are gone, Dunn specu- through” (as in, for example, “a river cours- other herbivores, but, in addition, an even lates, traits related to speed “may be cost- es through the valley”), and as a noun, the greater variety of predators. The American ly… The individuals that run the fastest ground covered (as in a race course). grasslands were more wild and ferocious may die younger, exhausted from fleeing It’s ironic that a word long used by an- than the African plains. The predators that ghosts but unable to slow down.” the ‘runner’s high.”’ Endocannabinoid sig- thropologists (and nobody else) to describe the earliest immigrants to America found On the other hand, homo sapiens are nalling in the hypothalamus, the nucleus animals capable of running long distances, as they colonized the continent fourteen- way more lethal than the dire wolf and the accumbens and other areas of the brain as- atrocious panther.) sociated with reward is at least partly re- The investigators’ underlying question: “why early hominids, for whom sponsible for the “high” reported by many The Pronghorn Principle running would have been much more difficult based on their skeletal anat- athletes during and after a vigorous work- “The pronghorn principle,” Dunn gener- out. omy, would have engaged in behaviors that are energetically taxing and alizes, “has two elements: First, all species Previous studies at UC Irvine had pro- increase the chance of injury in a predator-rich world?” have physical characteristics and genes vided some unexpected support for this that relate to the ways in which they inter- idea, using mice that had been bred over now evokes the image of an animal sitting or-more thousand years ago were bigger, act with other species. Second, when those many generations to engage in very high on its butt while manipulating a little item badder, and faster than anything we know other species are removed, such features levels of wheel-running exercise. Mice on the computer screen. I had just encoun- today There were plundering dogs (Bo- become anachronistic or worse. Plants are not naturally “cursorial,” but these tered “cursorial” in a piece about prong- rophagus spp.) short-legged dogs (Proto- have evolved toxins to defend their leaves, specially-bred mice would cover several horn (Antilocapra Americana). cyin spp.), dire wolves (Canus dirus), gi- nectar to entice animals to carry their pol- kilometers every night. When the Irvine According to pop-sci writer Rob Dunn, ant cheetahs, giant cave lions (Panthera researchers used the drug Rimonabant to pronghorn “at medium distances… may atrox), several kinds of sabre-toothed cats, block their endocannabinoid systems, the well be the fastest animal ever to have giant short-faced bears (Arctodus simus), mice reverted to more typical, low-exer- lived.” Dunn’s book “The Wild Life Of and other toothy monsters, many of them cise behavior. Our Bodies,” describes some intriguing fast. The cave lion grew to twelve feet in These findings suggested that artificial but unproven hypotheses about how inter- length. The saber-toothed cat could weigh selection through a laboratory breeding acting species have co-evolved. His open- 1,000 pounds and the giant short-faced program could lead to the evolution of ing chapter discusses the possibility that bear as much as 2,500 pounds. Most rel- running behaviors by specifically boosting the wipe-out of our intestinal parasites by evan to the story of the pronghorn, though, genes of the brain’s endocannabinoid sys- modern hygiene and antibiotics has led to was the American cheetah (Miracinonyx tem that get blocked by Rimonabant. a rising incidence of Crohn’s disease (be- trumani), a big, long, fast cat built to chase Raichlen and Gerdeman got a grant from cause under-employed digestive juices at- and catch at high speeds. Analogies with the National Science Foundation to study tack the lining of the gut). modern African cheetahs suggest that the whether a similar phenomenon occurs in Dunn continues: “There was precedent American cheetah would have loved to eat dogs (running animals), ferrets (sedentary for the idea that one species, such as a hu- pronghorn the way African cheetahs love len, and fruits to attract other animals to animals), and homo sapiens (running for man, might miss another species, even one antelope… carry their seeds. Animals, in turn, evolved countless eons as we evolved, but increas- long tongues to reach nectar or better sens- ingly sedentary in recent generations). Did es of smell to detect fruit. carnivores have natural selection also work through the long, sharp teeth to kill their prey. Intesti- genes of the endocannabinoid system to nal parasites have appendages that mirror, promote the evolution of running behav- in their contours, the guts of their hosts, to iors? Are human beings “wired to run?” hang on. Their team took blood samples from “Pick any organism on Earth and as the test subjects before and after vigorous much of its biology is defined by how it workouts on a treadmill. They determined interacts with other species as is influenced that anandamide levels rose significantly by the basics of living, eating, breathing, in people and dogs, but not in ferrets. In and mating. Interactions among species humans, the concentrations of anandamide (what ecologists call interspecific interac- in blood were tightly correlated to subjects’ tions) are part of the tangled bank to which improvement on a psychological question- Darwin referred… The consequences of naire assessing positive emotional well-be- removing the species our bodies evolved ing, thus supporting the possible causality to interact with, be they predators (as in between cannabinoid-receptor activation the case of the cheetah), mutualists like and the “runner’s high” (broadly interpret- the animals that once dispersed the giant ed as a state of elevated mood). American fruits [papayas, avocados, gua- On the other hand, non-strenuous ac- va, charimoya et al] or even parasites and tivity such as walking did not raise anan- Pronghorn are not antelope, deer or sheep but a species unto themselves. Photo by Mark Gocke disease.”