This image shows the differences in the position of the shoulder between chimpanzees (left) and humans (right). These differences can be seen in both the muscular anatomy and in the bony anatomy of the scapula (shoulder blade).
This allows humans to store elastic energy (like a slingshot) in the tendons, ligaments, and muscles crossing the shoulder. This energy is then used to catapult the arm forward in a fast motion, which allows very rapid throws. This was made possible by changes in the upper body that appeared first almost 2 million years ago in the species Homo erectus. This allows humans to throw projectile missiles (such as rocks and spears) with deadly speed and accuracy (Roach et al. 2013). Today, we see that most clearly in professional baseball pitchers who can throw baseballs at 90 to 100 miles an hour, again and again. By contrast, chimpanzees trained to throw can throw a ball only about 20 miles per hour, even though adult chimpanzees are physically stronger in some ways that adult humans.
This capacity for killing at a distance also helped our human ancestors to punish other humans in exercising what John Locke called "the executive power of the law of nature." Locke recognized that punishment could be costly for the punisher, because "such resistance many times makes the punishment dangerous, and frequently destructive, to those who attempt it" (ST, sec. 126). The costs of punishment come mostly from provoking violent attacks from those who are being punished. So the power to punish could never be effectively executed until the risky costs of punishment could somehow be reduced, so that the immediate costs of coercive punishment could be less than its immediate benefits in enforcing social cooperation.
Locke never explains how this could have happened. One likely explanation is that human beings became the first animals capable of killing at a distance by throwing rocks at their victims. Once this developed as a technique for hunting large animals, it could then be used to kill or threaten other humans who deserved punishment. Many people could throw stones at a misbehaving individual, and the punishers could do this with little risk to themselves. Thus the evolved human power to punish violators of the law of nature through killing at a distance could be a crucial evolutionary adaptation for Lockean liberalism. The expansion of social cooperation enforced by cheap punishment of cheaters has evolved from the expanding range of the weapons for remote killing--from rocks to bow-and-arrow to guns to nuclear bombs.
Anthropologists studying nomadic hunter-gatherers have recognized their remarkable egalitarianism--that all adult individuals are equally free in their autonomy and freedom from domination by others. This looks like Locke's state of nature. Anthropologists have seen that this egalitarianism requires "leveling mechanisms"--means by which individuals can prevent bullies from dominating them.
One of the critical leveling mechanisms is the equal access to weapons for remote killing. Anthropologist James Woodburn (1982) noted that in hunter-gatherer bands, all males have equal access to weapons. "Hunting weapons are lethal not just for game animals but also for people. There are serious dangers in antagonizing someone: he might choose simply to move away, but if he feels a strong sense of grievance that his rights have been encroached upon he could respond with violence" (436). Some men will try to dominate others by giving orders or by stealing wives and property, but this is punished by violent retaliation. Woodburn observes: "In normal circumstances, the possession by all men, however physically weak, cowardly, unskilled or social inept, of the means to kill secretly anyone perceived as a threat to their own well-being not only limits predation and exploitation; it also acts directly as a powerful levelling mechanism." For Thomas Hobbes, this was the ground for equality in the state of nature: despite all the inequality in human traits, no one was so superior as to be free from the threat of being killed by those he might try to dominate.
Biologist Paul Bingham has developed this idea into a general theory of human social evolution (Bingham 1999, 2000; Bingham and Souza 2009; Okada and Bingham 2008). Humans are unique because they are the first animals to be able to kill adult members of their species remotely. Every other unique feature of humans--such as language, abstract reasoning, morality, and so on--is simply an effect of that one cause.
Bingham argues that the uniquely human capacity for killing at a distance explains the uniquely human capacity for kinship-independent social cooperation. The evolution of all organisms creates the problem of conflicts of interest that impede social cooperation, because all organisms must compete for the resources necessary for survival and reproduction. A common way to manage those conflicts of interest is to cooperate with close kin, because kinship creates overlapping interests. So animals cooperate with close kin, and cooperation with non-kin is typically very limited. So, for example, among mammals, mothers commonly care for their offspring. Some animals--such as social insects--cooperate in huge colonies, but this depends on kinship: in ant and bee colonies, most of the (female) members of the colony work to rear their sisters (and a few brothers).
Like other animals, humans cooperate with their kin, but they also cooperate with non-kin much more expansively than is the case for other animals. To do this, they must manage the problem of conflicts of interest. And they do that by employing the cheap punishment made possible by remote killing to enforce cooperation: cheaters and free-riders are deterred from their misbehavior by the costs of punishment.
There is a lot of archaeological, anatomical, and ethnographic evidence to support this theory that the uniquely human capacity for throwing stones to kill from a distance initiated the uniquely human evolution of kin-independent social cooperation in a manner that sustains Lockean liberalism (Bingham and Souza 2009, 147-204; Isaac 1987; Marzke et al. 1988; Aiello and Dean 1990; Roach et al. 2013).
Beginning around 2.3 to 2.5 million years ago, there are archaeological deposits in East Africa of stone flakes and fossil prey bones indicating the evolution of hominid scavenging and hunting. There is also evidence of the evolution of elite human throwing associated with this early scavenging/hunting. There are piles of stones that archaeologists call "manuports" because the archaeological context suggests that they were moved across the landscape. Some of these manuports are of the size and shape that would make them good ammunition for throwing at prey animals or at other humans.
There is also skeletal evidence that the first fully human ancestors emerging about 2 million years ago had evolved the anatomical traits--in the hands, arms, torso, pelvis, and feet--that make humans uniquely good throwers. The hands and arms of our primate ancestors are adapted more for climbing than for throwing, because they were adapted for an arboreal life.
Darwin noticed how skillful hunter-gatherers in Tierra del Fuego were in throwing stones forcefully and accurately. By contrast, he saw that monkeys and apes were clumsy throwers. He thought this was one uniquely human trait arising from bipedality and the design of the human hand and arm, which might help to explain human dominance over the Earth (Darwin 2004, 68-72).
Other European explorers of the New World and the South Pacific discovered how deadly this rock throwing could be, because aboriginal people could attack European intruders with a bombardment of stones (Isaac 1987).
If Bingham is right, that evolved uniquely human capacity for elite throwing was the cause for the evolution of the big human brain that arises from a uniquely human life history that depends upon human kin-independent social breeding (Bingham and Souza 2009, 120-146). "It takes a village to raise a human child," and unlike the social breeding of other animals, the human village that helps in the rearing of offspring includes many adults of both sexes who are not close kin. It also includes many adult members who are armed for the projection of coercive threat that enforces the village's non-kin cooperation.
A newborn chimp has a very big and heavy brain. But a newborn human has an even bigger and heavier brain. Moreover, the human infant's brain will grow much faster and longer. This growth will extend even into young adulthood. And while a chimp mother can provide enough food and care for her offspring by herself, a human mother must provide so much more food and better food and so much more care for her offspring that she cannot do this without help from others. A human mother needs to be a member of a large society--at least as large as a foraging band--that will help in the rearing and protection of her child. And this society will extend beyond her kin to include unrelated adults. That's why "it takes a village to raise a human child."
But then we might wonder why the help of her husband would not be enough for her. Maybe, "it takes a couple to raise a child!" That's Locke's solution to the mother's problem. He argues that like many birds, human beings are pair-bonding animals because mothers need the help of fathers in providing food, rearing, and protection for the children, when mothers alone cannot do this. Human beings are naturally cooperative breeders in families of mothers, fathers, and children (FT, secs. 86-89; ST, secs. 77-84). Some evolutionary anthropologists today support this idea--that pair-bonding is the crucial evolutionary adaptation in human evolution.
But this doesn't explain why other pair-bonding animals like birds didn't follow the human evolutionary path towards large communities of non-kin members. And it doesn't explain why human pair-bonded families depend on the support of that large community of both kin and non-kin members.
The proper explanation, Bingham suggests, is that humans are unique in their capacity for non-kin social cooperation, which supports the uniquely human life history for sustaining the growth and rearing of that big human brain. Non-kin cooperation is impossible without some way to manage the conflicts of interest that necessarily arise among individuals who are unrelated to one another. Humans are unique because they stumbled into a clever trick for managing such conflicts of interest by the low-cost punishment of cheaters and free-riders through killing or threatening to kill them from a distance.
In foraging bands, most or even all adult individuals have access to such coercive threat, which has a levelling effect in securing each individual's autonomy and freedom from domination. Consequently, power is democratized in foraging societies, and social norms are formulated and enforced through a broad consensus.
But then, Bingham argues, with the emergence of archaic states, coercive power was concentrated in ruling elites that could enforce their will on the great multitude. To restore or at least approximate the equal liberty of the hunter-gatherer society--what Locke called the state of nature--access to the weapons of coercive threat would have to be once again equalized.
Here Bingham has rediscovered an insight of some political philosophers--that the structure of political order depends on whether the access to weapons of coercive power is confined to a few or open to many. In the Politics, Aristotle writes:
"Since there are four parts of the multitude, the farming, the working, the merchant, and the laboring elements, and four parts of the city are useful with a view to war, the horse-rearing, the heavy-armed, the light-armed, and the seafaring elements, wherever it happens that the country is suitable for horses, conditions are naturally apt for instituting a strong oligarchy (for the preservation of the inhabitants derives from a force of this sort, and horse-rearing is done by those possessing larger properties); where it is suitable for heavy arms, the next sort of oligarchy (for the heavy-armed element is made up of the well off more than the poor). Light-armed and naval forces, on the other hand, are wholly popular. At present, therefore, wherever this sort of multitude is numerous, and there is a factional split, the oligarchs often get the worst of the contest. . . . This is the way the people prevail over the well off in factional splits: being light-armed, they can easily contend against a force of cavalry and heavy-armed troops" (1321a5-21).
Aiello, L., and C. Dean. 1990. An Introduction to Human Evolutionary Anatomy. San Diego: Academic Press.
Bingham, Paul. 1999. "Human Uniqueness: A General Theory." Quarterly Review of Biology 74: 133-69.
Bingham, Paul. 2000. "Human Evolution and Human History: A Complete Theory." Evolutionary Anthropology 9: 248-57.
Bingham, Paul, and Joanne Souza. 2009. Death from a Distance and the Birth of a Humane Universe. Charleston, SC: BookSurge Publishing.
Darwin, Charles. 2004. The Descent of Man. 2nd edition. London: Penguin Books.
Isaac, Barbara. 1987. :"Throwing and Human Evolution." The African Archaeological Review 5: 3-17.
Marzke, M. W., et al. 1988. "Gluteus Maximus Muscle Function and the Origin of Hominid Bipedality." American Journal of Physical Anthropology 77: 519.
Okada, D., and Paul Bingham. 2008. "Human Uniqueness--Self-Interest and Social Cooperation." Journal of Theoretical Biology 253: 261.
Roach, Neil T., et al. 2013. "Elastic Energy Storage in the Shoulder and the Evolution of High-Speed Throwing in Homo." Nature 498: 483-86.
Woodburn, James. 1982. "Egalitarian Societies." Man 17: 431-51.