Book Excerpt from Rough and Tumble

But, those same experienced hunters, who hunt as an integral part of their livelihood, have a mostly deliberate approach to the act of killing prey—even if that approach might arguably be guided by “a thirst for the jubilation of the seek-and-kill experience.” It’s not hard to grasp the reasons for this carefully calculated type of hunting. Living off the land, as do traditional foragers, is an unforgiving enterprise, subject to vagaries that almost never touch the insulated lives of urbanized Western people. Real nature rarely suffers fools. Inclement weather, lurking predators, and even simple infections are all potentially mortal eventualities in the daily life of a hunter-gatherer. Likewise, the dis­tribution, abundance, and availability of food across space and time shape a hunter’s foraging decisions, and those decisions, in turn, affect survivorship for him, his family, and his social group. In that kind of system, an animal carcass—with its dense concentration of nutrients and calories, in the form of skin, meat, marrow, and brain tissue—is the highest-ranked (or second-highest-ranked, with delicious, sugary honey sometimes topping it) among a capriciously oscillating range of food choices. It is true that locating this top-ranked resource some­times involves a good degree of providence. But, more often it is cool-headed calculation—in, for example, patiently manning a hunting blind along a predictable game trail; in taking a careful, one-chance-only shot with the bow; or, in knowing when to abandon tracking a nonfatally wounded animal in favor of a more reliable fallback plan—that yields the greatest dividends for the hunter.

For men in traditional societies, hunting success also means some­thing beyond mere subsistence. It confers status, because as a top-ranked food, animal product is as desired by women as it is by men. But, because most hunter-gatherers practice a sexual division of labor, women are usually relegated, day in and day out, to the tedium of plant foraging; often, as in the case of many subtropical African foragers, this means having to bend over a sharpened wooden stick for two or three hours a day of back-breaking digging in order to excavate deeply buried tubers, which serve as important (and flavorless!) dietary staples. Thus consigned, most forager women must rely on male hunters to share meat and marrow with them. Obtaining nutrient-laden, energy-packed meat and marrow contributes to a woman’s and her dependent offspring’s good health and survivorship. Thus, a proficient hunter’s high status, in turn, holds the potential to be converted into increased Darwinian fitness—but the ways in which that happens are not always as direct as male–female exchange of meat for sex. In some foraging groups, good hunters do enjoy higher frequencies of extramarital matings than do poorer hunters, but the complexity of modern human culture ensures that the evolutionary advantage of being a skilled hunter is more nuanced in most cases. Research among a group of northern Tanzanian hunter-gatherers, the Hadza, illustrates the point: the best Hadza hunt­ers have younger, more fertile, and harder-working wives than do less successful hunters. In other words, a Hadza man’s predatory prowess is linked to his success in attracting the best mates—those women who, in other words, will have the highest number of viable offspring and who will work hardest at ensuring the survivorship of those offspring.

Expertise in hunting the large, warily dangerous prey of human foragers and cashing in on its concomitant evolutionary rewards does not mature from the hell-bent approach employed by chimpanzees to dispatch their prey. Application of brute physicality is an efficient means for chimpanzees to kill because they hunt in groups, they concentrate on much smaller animals than themselves, and they rely on their super­human strength and agility to overpower their victims; an adult male chimpanzee is at least as twice as strong as a grown man, and chimpan­zees make many of their kills on monkeys high in the forest canopy. A human has no hope of out-muscling, out-running, or out-climbing his typical prey, but, if his mind stays clear, he can absolutely count on out-thinking those animals.

Indeed, it might be that part of the long-term evolutionary trade-off for the increasing growth of the human brain through time was conces­sion of some muscular power. Paleogeneticist John Hawks muses about intriguing new data emerging from genomics:

Even though chimpanzees weigh less than humans, more of their mass is concentrated in their powerful arms. But a more important factor seems to be the structure of the muscles themselves. A chimpanzee’s skeletal muscle has longer fibers than the human equivalent and can generate twice the work output over a wider range of motion. In the past few years, geneticists have identified the loci for some of these anatomical differences. One gene, for example, called MYH16, contributes to the development of large jaw muscles in other apes. In humans, MYH16 has been deactivated. (Puny jaws have marked our lineage for at least two million years.) Many people have also lost another muscle-related gene called ACTN3. People with two working versions of this gene are overrepresented among elite sprinters, while those with the nonworking version are overrepresented among endurance runners. Chimpanzees and all other nonhuman primates have only the working ver­sion; in other words, they’re on the powerful, “sprinter” end of the spectrum.

Hawks develops the theme elsewhere: “Genetics may be starting to make the ‘expensive tissue’ story [see chapter 1] come down to muscle instead of gut reduction—if I’m going to make predictions, I would say that MYH16 will not long be alone as a gene corresponding to human muscle reduction.”

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Reprinted from Rough and Tumble: Aggression, Hunting, and Human Evolution, by Travis Rayne Pickering. Copyright © 2013 by Travis Rayne Pickering. Reproduced with permission from the University of California Press.