Letâs begin with a story, recognizing itâs just a storyâŠ
Somewhere in Africa, some 6â10 million years ago, during the late Mioceneâa period of gradual cooling and drying marked by shrinking forests and expanding grasslandsâtwo small-brained, somewhat bipedal apes, daughters of the same mother, parted ways.
One sister wandered off with a band that ventured deeper into the receding jungle. Partly because her group specialized in gathering the fruits and tender young leaves so freely available in the treetops, their legs grew shorter over time and more powerful, the better for shimmying up tree trunks. Their toes and fingers grew longer, the better for grasping branches, but not so good for walking upright or the fine manipulation of tools. For safety, they slept in trees at night. When they descended to the ground during the day, they retained an ability to walk on two legs for short distances, but, like their cousins the gorillas, they came to rely on an awkward four-legged gait, supporting themselves in front with their knuckles.
In sexual matters, females on this sisterâs side of the family pursued a clever âhave your cake and eat it tooâ strategy: they mated with multiple partners during periods of relatively low fertility and then grew more selective during their much shorter periods of maximum fertility. In this way, females built useful affiliations with multiple males and at the same time exerted reasonable control over the fate of their own genes. For their part, males competed aggressively with each other for sexual access to willing females, taking on as many as would have them. However, given the paternity confusion resulting from their promiscuity, they had no reason to protect and provision particular females or even their own offspring. As a result, the males remained self-serving bachelors, leaving the females to forage alone for themselves and their young ones.
Like many other primates, males and females continued to manipulate and maintain their social relationships with other group members using a combination of snarling, aggressive displaysâfeaturing their enlarged, sharpened caninesâand, in their more peaceful hours, strengthening their affiliations by carefully stroking and plucking each otherâs scaly, parasite-ridden pelts. They learned (by observing others) how to use rocks and sticks as foraging tools, but they never learned how to sharpen a stone and attach it to the end of a stick.
Like all primates, these animals sought to shape each otherâs behavior using a rich repertoire of facial expressions, physical gestures, and vocalizations, sometimes for the benefit of others, as in the case of alarm calls, but more often for their own selfish purposesâto obtain food or sex or to frighten away competitors. And for some reason, perhaps for the same reason, it seems these creatures never developed the capacity to peer inside each otherâs minds, to imagine the inner life, beliefs, and mental perspectives of another thinking being like themselves, or to consider the difference between their own beliefs and those of others. As a result, like all animals, they continued to be good learners, but, unlike some, they never engaged in anything much resembling intentional instruction. Today, we call this sisterâs descendants chimpanzees.
The other sisterâs band pursued a radically different pathâan extraordinary, high-risk evolutionary journey that would eventually take twelve of her descendants to the cratered surface of the moon and back. As the journey started, these creatures began to forsake the relative safety of fruit-bearing trees in the shrinking rainforests for a riskier but potentially more prosperous life as itinerant foragers in the expanding woodlands, grassy savannas, river valleys, and other waterside habitats that had begun to appear in the wake of the receding jungles.
Along the way, something especially strange happened in the brains and bodies of these increasingly bipedal apes. Instead of mating freely with multiple partners, individual males and females began finding themselves attracted to special someones, often the brainier ones. Forsaking their earlier promiscuity, they began forming increasingly strong, relatively permanent bonds with their lovers, formed extended family groups, and began raising children together. No longer competing directly with other males for access to sex, and thereby freed from the need to keep a watchful eye on all the females in their groups, males came to engage in cooperative, increasingly long-distance foraging expeditions, returning to a base camp at the end of the day with food to share with their mates, children, and extended family members.
Partly because of the new social arrangements and division of labor, these creatures became better fed, lived longer, and began to expand their numbers. Most consequentially, nourished by their new diet, and in response to the new cognitive demands of family living, their brains began to grow larger in proportion to the rest of their bodies, eventually, over millions of years, tripling in size. As a result, and under building pressure to feed their burgeoning, energy-hungry brains, these animals, male and female alike, became increasingly skillful, opportunistic omnivores, learning to extract and process the wide variety of highly nutritious but difficult-to-acquire foods they discovered in their expanding territories: underground tubers, shellfish buried in mud, marrow hidden in the bones of scavenged carcasses left unattended by the original killers.
And as their brains grew bigger, they began to apply their intelligence in new ways. They learned to exploit the fracture properties of basalt and other volcanic rocks, knocking one rock against another to split off sharp flakesâgood for sharpening sticks and stripping flesh from carcasses. Their hands, already equipped with shorter fingers and opposable thumbs, became increasingly adapted for gripping and precisely manipulating these new tools. Eventually, they learned to collectively track down and kill large animals, to control fire, to haft sharpened stones to sticks, to make boats and nets, to manufacture assault rifles. In the process, they damaged untold numbers of habitats, and directly or indirectly caused the extinction of untold numbers of other species.
Most remarkably, and long before assault rifles, these creatures had somehow grown what amounted to a kind of âthird eyeââa highly evolved system of neural circuitry (grown from wiring inherited from their own primate ancestors) which allowed them to peer, with increasing acuity, into the minds of other members of their groups and imagine, however imperfectly, the perspectives and beliefs of a fellow thinker. At the same time, they became increasingly altruistic, willing to share information for the common good. They began directing each otherâs attention, by pointing with their fingers, to objects and events of mutual concern in the immediate environment: a leopard in a tree, the tracks of other animals, distant food patches, the best place to hit a rock to strike off a sharp flake. Under pressure to communicate their beliefs and intentions more accurately and efficiently, they began to develop an increasingly sophisticated set of signals, in which certain conventionalized combinations of gestures, facial expressions, and vocalizations could be used to signal meanings quickly, with increasing precision. Eventually, these signals came to have internal, brain-based representations with both internal (mental) and external (real-world) referentsâan expanding set of linguistic symbols. All manner of meanings could now be shared. Gestures and vocalizations could be used, not just to frighten and summon, but to convey helpful information: âAntelope carcass over there.â And to direct the behavior of others: âYou go that way. I stay here.â
Because individuals who were even slightly better at using the new signaling system became better fed, better at attracting mates, and better at raising children to maturity, the genetic programs that made them better communicators and better mind readers spread throughout their populations. The new signaling systemâlanguageâhad become part of their environment and had begun to shape the brains of its users for its own purposes.
Over millions of years, the nearly infinite complexity of the natural worldâand the advantages that accrued to those who could better organize this complexity in their own minds and the minds of othersâcreated pressure for ever more sophisticated and efficient versions of language. Along the way, the creatureâs vocal and auditory systems became specialized for high-speed speech, capable of producing and interpreting strings of phonemes (speech sounds), representing an infinite number of possible meanings, at the rate of 10â15 per second.
The coevolution of brains, technology, and language had produced an animal with an entirely new way of thinking and communicating about the world with others, of engaging in joint activities for the common good, and of efficiently transmitting hard-won, life-sustaining knowledge and skill from experts to novices, down through the generations. The second sisterâs descendants had become a new species of talking, teaching apeâthe most ingenious species on Earth, and the most dangerous. They had become us.