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January 22 - February 24, 2021
Bonobos are the rarer, less well-known cousins of chimpanzees that live only in remote forests south of the Congo River in Africa. But unlike male chimpanzees and gorillas, male bonobos rarely engage in regular, ruthless, reactive violence. Whereas male chimpanzees frequently and fiercely attack each other to achieve dominance and regularly beat up females, male bonobos seldom fight.37 Bonobos also engage in much less proactive violence. Experts hypothesize that bonobos self-domesticated because females were able to form alliances that selected for cooperative, unaggressive males with lower
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Many scientists are testing the idea that humans also self-domesticated.40 If so, I’d speculate this process involved two stages. The first reduction occurred early in the genus Homo through selection for increased cooperation with the origins of hunting and gathering. The second reduction might have occurred within our own species, Homo sapiens, as females selected for less reactively aggressive males.
hoplology
Like chimpanzees, early hominins must have employed simple wooden tools, but a seismic shift happened sometime between 3.3 and 2.6 million years ago with the invention of stone tools, about the same time as the oldest evidence for meat eating.
Further, untipped spears do not create as much tissue damage as spears with stone points, an innovation that dates to only 500,000 years ago.
When Neil and I looked at the fossil record, we noticed that all the features that enable us to throw well show up by two million years ago in the species Homo erectus.62 Given that humans also started hunting around then, throwing capability was probably selected to help put meat on the table. It would be naive, however, not to suppose that early hominins sometimes also threw spears or rocks at each other as well. I suspect H. erectus children spent hour upon hour practicing their throwing skills and developing upper-body strength. All over the planet,
Consider fire and clothing. With these inventions, hominins were able to move into new, colder environments that then permitted selection for features like lighter skin away from the tropics.
Since cooking became common, human digestive physiology evolved to make us now
dependent on cooking t...
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First spears. Beyond our adaptations for throwing, recall that males in the human genus shrank from being about 50 percent to just 15 percent bigger than females. Much of that size reduction is probably explained by less male-male competition, but we cannot rule out the possibility that spears diminished the benefits of having a big body when hunting or fighting.
A more speculative hypothesis is that the invention of the bow and arrow and other cutting-edge projectile technologies revolutionized the costs and benefits of reactive aggression. For the first time, slight Davids like me could take down Goliaths, and females could defend themselves more effectively against male aggressors. Weapons like the bow and arrow also helped less brawny individuals hunt effectively and with reduced risk at a distance. Since the bow and arrow was invented 100,000 years ago, it has probably been less advantageous to be big and reactively aggressive.67 Wouldn’t it be
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Achilles’s message exemplifies Richard Wrangham’s argument: the Greeks need to stop fighting among themselves and instead cooperate if they are to end their ten-year siege. They should stop being reactively aggressive with each other and be only proactively aggressive toward the Trojans. As with war, suppressing reactive aggression and following rules are fundamental to most sports.
In the final analysis, humans are physically weaker than our ancestors not because we evolved to fight less but because we evolved to fight differently: more proactively, with weapons, and
Along the same lines, we didn’t evolve to do sports to get exercise.
As a form of organized, regulated play, sports were developed by each culture to teach skills useful to kill and avoid being killed as well as to teach ea...
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And then our walk changed thanks to a honeyguide bird. These little brown birds have been collaborating with humans in Africa for thousands, possibly millions of years.1 In typical fashion, the honeyguide loudly tweeted out its distinctive, insistent, chattering song—tch, tch, tch tch, tch, tch!—and then flew from tree to tree singing periodically to make sure we followed. Within ten minutes our little friend delivered us to a beehive.
But mostly they walk. If there is one physical activity that most fundamentally illustrates the central point of this book—that we didn’t evolve to exercise but instead to be physically active when necessary—it is walking.
Every year, the average hunter-gatherer walks the distance from New York to Los Angeles. Humans are endurance walkers.
downwardly oriented foramen magnum.
The woeful inefficiency of knuckle walking is rarely a problem for chimpanzees deep in the forest, but it must have been a serious challenge for our missing-link ancestors about seven to nine million years ago. During this period of rapid climate change, the rain forest that covered much of Africa shrank and split into thousands of fragments interspersed with drier, open woodlands. For apes living in the depth of the rain forests, life went on as usual, but those at the margins of the forest must have faced a crisis. As woodlands replaced the forest, the fruits that dominated their diet became
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To fathom just how advantageous it is to walk upright instead of knuckle walk like an ape, let’s return to that morning I spent with Bagayo and Hasani. That 7.4-mile walk likely cost me a respectable 325 calories. However, if I were as inefficient as a chimpanzee, the walk would have cost me roughly 700 calories. By walking upright instead of knuckle walking, hunter-gatherers like Bagayo and Hasani save more than 2,400 calories per week, adding up to 125,000 calories a year. That’s roughly enough energy to run about forty-five marathons.
The forces that drove our ancestors to walk upright eons ago may seem irrelevant today, but they aren’t. For millions of years until the postindustrial era, our ancestors had to walk something like five to nine miles every day to survive. We evolved to be endurance walkers. Yet, like our ancestors, most of us retain a deep-seated drive to spend as little energy as possible by walking only when necessary. That instinct to conserve calories points to another key difference between walking today and in the past: how much we carry things like babies, food, fuel, and water.
The majority of dieters who do not exercise regain about half their lost pounds within a year, and thereafter the rest typically creeps back slowly but surely. Exercise, however, vastly increases the chances of maintaining weight loss.
(To set the record straight, Pheidippides’s death was invented seven hundred years later and popularized by the nineteenth-century poet Robert Browning to add pathos to his poem’s climax; it was never mentioned by Herodotus or other ancient historians who wrote accounts of the event.)
Our conversation quickly turned to the importance of stabilizing one’s gaze and the hypothesis that animals adapted for running (“cursors” in biological parlance) have a special rubber-band-like structure, the nuchal ligament, at the back of their heads that acts like a spring to keep their heads still. As soon as that pig was back in its pen, Bramble and I were looking at skulls
“Endurance Running and the Evolution of Homo,” and the magazine’s cover, which featured our paper, was emblazoned “Born to Run.”4 Our basic argument was that by two million years ago our ancestor Homo erectus had evolved the necessary anatomy to run long distances in the heat in order to scavenge and hunt long before the invention of bows and arrows and other projectile weapons.
At some point, humans evolved a magnificent cooling system by taking advantage of special water-secreting glands that most animals have only on their paws. Monkeys and apes have small quantities of these so-called eccrine glands elsewhere on their bodies, but we alone have five to ten million sweat glands all over our skin, especially on our heads, limbs, and chests.
Sweating effectively turns the entire body into a giant, wet tongue.
Almost all the features I just reviewed that help humans run are what biologists term convergent, which means they evolved independently in humans and other animals adapted for running. However, because we are unsteady bipeds that evolved from tree-climbing apes, running humans are uniquely prone to falling. A slight shove or an unfortunately placed banana peel is more likely to topple a running human than any quadruped. Because a sprained ankle or broken wrist could be a death sentence in the Stone Age, it makes sense that humans evolved a suite of unique and crucial features for
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But these are very modern attitudes. No hunter-gatherer spurns the chance to obtain free meat even if it isn’t very fresh, and hunting is a highly valued way to acquire nutrient-rich food and achieve status. Yet until relatively recently, scavenging and hunting were difficult, dangerous, and almost impossible to do without running.
Hominins probably first started to eat meat by scavenging, yet by 2 million years ago there is clear archaeological evidence that they also hunted large animals like wildebeests and kudu.
This is easier said than done without serious weapons. The bow and arrow was invented less than 100,000 years ago, and putting stone points on spears was invented maybe 500,000 years ago.26 Before these weapons, hominin hunters would have had to get close to their prey, sometimes by thrusting spears into them. Please don’t try this. Meat is a nutritious food, but given the risk of being kicked or gored while getting up close and personal with an angry wildebeest, it’s remarkable that more of our hunter-gatherer ancestors weren’t vegetarian.
This cat-and-mouse game of chasing, then tracking, is repeated again and again. Assuming the hunters resume the chase before the animal fully cools, its body temperature will gradually keep rising until, eventually, it reaches a state of heatstroke and collapses. A hunter can then walk right up to the animal and dispatch it safely without sophisticated weapons (sometimes using just a rock).
Unsurprisingly, almost no one persistence hunts anymore unless they are obliged to like Alexander Selkirk, the inspiration for Robinson Crusoe, who ran down feral goats while marooned on a South American island.
As a shoe’s elasticity deteriorates, the built-in arch support loses effectiveness, putting extra strain on the plantar fascia. So I rushed to my local running shoe store, bought new shoes, and the problem gradually cleared up. After that, I made sure to buy new shoes every three months despite the expense.
We speculated that humans evolved primarily to forefoot strike when running, and called for research to test if this running style, common among elite runners, might prevent injuries.
We should do everything we can to prevent runners from getting hurt, but it also behooves us to puncture some pervasive myths about running injuries, the biggest of which is that wear and tear from hoofing too many miles will erode the cartilage in your knees and hips and give you osteoarthritis. Not so. Despite what many doctors and others assume, more than a dozen careful studies show that nonprofessional runners are no more likely to develop osteoarthritis than non-runners.44 In fact, running and other forms of physical activity help promote healthy cartilage and may protect against the
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IT bands, and other vulnerable tissues can adapt. Many experts thus advocate increasing mileage only 10 percent a week.46
The muscles alongside the hip (termed hip abductors) that prevent the knees from collapsing dangerously inward during every step are a notorious weak link.48
Good running form (on right) compared with common poor form (left).
agree on four key, related elements illustrated in figure 25: (1) not overstriding, which means landing with your feet too far in front of your body; (2) taking about 170–180 steps a minute; (3) not leaning too much, especially at the waist; (4) landing with a nearly horizontal foot, thus avoiding a large, rapid impact force with the ground.52
Avoid overstriding. Get your knees up when you swing your legs forward so you land with a vertical shank and your foot below the knee, not too far in front of the hips. This prevents the legs from landing too stiffly and causing overly high breaking forces that slow you down. Step rate usually increases with speed, but experienced endurance runners generally take 170–180 steps a minute regardless of speed. They thus speed up economically by jumping farther (running is jumping from one leg to another), and a high step rate prevents overstriding. Lean forward slightly, but not too much at the
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Land gently with your feet nearly horizontal. If you are barefoot and don’t overstride, it is almost impossible not to land on the ball of your foot before letting down your heel in what is called a forefoot or mid-foot strike. Forefoot and mid-foot strikes usually don’t generate an impact peak on the ground—a rapid, large collisional force that is painful without shoes. Forefoot and mid-foot strikes also generate rotational forces (torques) that are lower in the knee but higher in the ankle, requiring strong calf muscles and Achilles tendons, which can l...
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As the Norwegian explorer Carl Lumholtz remarked of the Tarahumara in 1905, “Dance with these people is a very serious and ceremonious matter, a kind of worship and incantation rather than amusement.”59 Even the infamously repressed English used to dance much more than they now do. In Jane Austen’s time, balls could go on all through the night. In Sense and Sensibility, Mr. Willoughby danced “from eight o’clock till four, without once sitting down.”60
do not quit playing because they grow old; they grow old because they quit playing.”
Human hunter-gatherers, in contrast, typically wean their offspring after three years and become pregnant again long before their little ones are able to feed or fend for themselves, let alone stay out of danger. A typical hunter-gatherer mother, for example, might have a six-month-old infant, a four-year-old child, and an eight-year-old juvenile. Because she is usually capable of gathering only about two thousand calories a day, she cannot get enough food to provide for her own substantial caloric needs, which exceed two thousand calories, as well as the needs of her several offspring, none
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Anthropologists have shown that grandmothers, grandfathers, aunts, uncles, and other older individuals in foraging populations from Australia to South America remain active throughout life, gathering and hunting more calories every day than they consume, which they provide to younger generations.13 This surplus food helps provide adequate calories to children, grandchildren, nieces, and nephews and reduces how much work mothers have to do.
generations. Once this novel cooperative strategy—the essence of the hunting and gathering way of life—started to emerge during the Stone Age, natural selection had the chance to select for longevity. According to this theory, hardworking and helpful grandparents who looked out for others and who were blessed with genes that favored a long life had more children and grandchildren, thus passing on those genes.
As a result, many of the mechanisms that slow aging and extend life are turned on by physical activity, especially as we get older. Human health and longevity are thus extended both by and for physical activity.
Another way of stating the active grandparent hypothesis is that human longevity did not evolve to enable elderly humans to retire to Florida, sit by the pool, and ride around in golf carts. Instead, old age in the Stone Age meant plenty of walking, digging, carrying, and other forms of
