So, for example, I have claimed that an evolutionary science of human nature can show that Thomas Hobbes was partly right, Jean-Jacques Rousseau was mostly wrong, and John Locke was mostly right about the state of nature. I have also claimed that Adam Smith was right about "the propensity to truck, barter, and exchange" as part of that evolved human nature, and that the liberation and honoring of that propensity in liberal commercial societies explains the Great Enrichment of the past two centuries, which has promoted the unprecedented flourishing of human life in the Bourgeois Era in which most of us now live.
There are at least three objections to this reasoning. The first is that there is no human nature, because there is too much cultural and individual variability in human existence to warrant any belief in an unchanging human essence.
The second objection is that anthropological studies of existing hunter-gatherers over the last two centuries shows such variability in their societies that it is impossible to generalize about the human nature of the foraging way of life.
The third objection is that even if it were possible to generalize about hunter-gatherers of the last two centuries, this would tell us nothing about our prehistoric hunter-gatherer ancestors, whose societies were variable in their adaptations to the social and physical environments of the prehistoric past.
I have replied to the first objection in my responses to David Buller (here) and Jesse Prinz (here). If one defines human nature in a silly way (as Buller does), then human nature does not exist. But if one defines human nature in a sensible way, then human nature surely does exist. A silly definition of human nature is that it must consist of traits that are eternal essences that are not historically contingent, so that they are invariably and exactly the same for all human individuals in all human societies. It is easy to argue that human evolution has not produced a human species with such traits.
But a sensible definition of human nature does not require these conditions. We could define human nature as constituted by those enduring (but not eternal) regularities in that suite of generally recurrent anatomical, physiological, and psychological traits that characterize the human species for as long as it exists. Although this suite of traits is generally recurrent across the human species, there will always be great variation across human individuals and across human societies. One can look at Gray's Anatomy and see the anatomical adaptations that generally characterize the human species, although every human individual is anatomically unique. Similarly, one can study human evolutionary psychology and see the psychological adaptations that generally characterize the human species, although every human individual is psychologically unique.
A biopolitical or biosocial science would have to move through three levels of deep history--the natural history of the human species, the cultural history of particular human communities, and the biographical history of individual actors in those communities. This is also true for other social animals. So that, for example, Jane Goodall's history of the chimpanzees of Gombe must be a natural history of the chimpanzee species, a cultural history of the chimpanzee community at Gombe, and a biographical history of the individual chimpanzees in the Gombe community.
The other two objections that concern the human nature of hunter-gatherers have been well stated by Robert Kelly in The Lifeways of Hunter-Gatherers: The Foraging Spectrum (Cambridge University Press, 2013), which is a revised version of The Foraging Spectrum: Diversity in Hunter-Gatherer Lifeways (Smithsonian Institution Press, 1995). This book is generally recognized as the best survey of the anthropological studies of hunter-gatherers.
Kelly observes that "anthropologists seek human nature," that they "think of hunter-gatherers as displaying human nature," and that they think that the anthropological studies of hunter-gatherers show "humanity in the state of nature," because they show what human beings were like in prehistoric foraging societies (xv, 272). Kelly denies all of this by arguing that the observable variability in hunter-gatherer lifeways subverts any idea of a universal human nature, and that what anthropologists have learned about living hunter-gatherers tells us almost nothing about prehistoric hunter-gatherers.
And yet, far from denying human nature, Kelly's book is actually organized around an implicit theory of human nature that is evident in the topics of chapters 3-9 of the book: (3) Foraging and Subsistence, (4) Mobility, (5) Technology, (6) Sharing, Exchange, and Land Tenure, (7) Group Size and Demography, (8) Men, Women, and Foraging, (9) Nonegalitarian Hunting-Gatherers. Why does he assume that these are the most important topics? Because they are natural human desires or needs that any human society must satisfy in some manner? If so, then why isn't this a matter of human nature?
Foraging and subsistence are prominent in the anthropology of hunter-gatherers, Kelly tells us in Chapter 3, because "without food, people die" (40). Doesn't this implicitly assume the human nature of the need for food? As Stephen Sanderson has indicated (in Human Nature and the Evolution of Society), making a living is a fundamental need of human nature, and there are essentially four ways of making a living: foraging for wild animals and plants (hunting, gathering, and fishing), herding domesticated animals, farming domesticated plants, and trading or commerce (buying and selling). Human social orders can be distinguished by the prominence of these ways of making a living--with human history showing a movement from foraging to farming to trading.
"Hunting and gathering, of course, is not all that hunter-gatherers do," Kelly observes. "They also spend time in religious activities and prestige competition, in family life, socializing, trading, defense, and tool manufacture" (108). This list of human concerns covers many of what I have identified as the 20 natural desires of evolved human nature: a complete life, sexual identity, sexual mating, parental care, familial bonding, friendship, social status, justice as reciprocity, political rule, war, health, beauty, property, speech, practical habituation, practical reasoning, practical arts, aesthetic arts, religious understanding, and intellectual understanding.
From Lewis Henry Morgan to Richard Lee, it has been common for anthropologists to argue that hunter-gatherers show "primitive communism" in their sharing behavior, and thus the ownership of property is not rooted in human nature. But in Chapter 6, Kelly concludes that while "hunter-gatherers appear to share food, goods, and access to land quite readily," "this is not simply primitive communism" (164). Hunters do share some of their meat, but they favor their family and their close kin. Moreover, in sharing their meat, hunters expect reciprocity from those who benefit from their reciprocity. Hunters who have shared their meat expect to be repaid in the future, when they return from an unsuccessful hunt and need others to share with them. Successful hunters derive prestige from their hunting and their sharing, and they have greater reproductive success. "Generous people do better in the long term than stingy people," Kelly explains (151). Land tenure is variable, but "boundaries exist" (154); and territoriality appears "when resources are sufficiently dense and predictable and, especially, where competition is high" (164). Doesn't this manifest the natural human desires for property, sexual mating, parental care, familial bonding, social status, and justice as reciprocity?
In Chapter 8, Keely observes that hunter-gatherers show a sexual division of labor, in which men do most of the hunting for large game, and women do most of the gathering of plants and hunt only small game. The main reason for this sexual division of labor is that gathering is more compatible with pregnancy, breastfeeding, and childcare. It is hard for women to hunt large game if they have to care for their children at the same time. Moreover, it is hard to learn how to hunt well, and it requires ten to twenty years of experience. It is easier for young men to acquire hunting skill than for young women, because young men are less involved in caring for children. This creates sexual differences in status, since hunting and sharing meat confers prestige on men. Women benefit from this insofar as wives benefit from the high status of their husbands. Men benefit from this insofar as the most successful hunters attract the best mates and have the highest reproductive rates. Don't we see here the natural human desires for sexual mating, sexual identity, parental care, and social status?
In considering sexual mating, Keely surveys the rules for marriage that determine whom one can and cannot marry (234-39). In some hunter-gatherer societies, cousin marriage is permitted or even encouraged; but in others, cousin marriage is prohibited. Although Keely does not explicitly mention it, no hunter-gatherer societies permit parents to marry their children or siblings to marry one another. Here we see a universal incest taboo that prohibits marriage within the nuclear family, although marriage outside the nuclear family depends on variable rules of kinship.
Edward Westermarck's Darwinian theory of the incest taboo explains this as a naturally evolved instinct to feel a sexual aversion to mating with those with whom one has been raised, which can be explained as an evolutionary adaptation to avoid the deleterious effects of inbreeding. This is one of the best developed examples of the evolutionary psychology of human nature.
In Chapter 9, Kelly explains the contrast between two kinds of foraging societies that anthropologists have called simple and complex. Simple foraging societies are small nomadic societies that are largely egalitarian, while complex foraging societies are large sedentary societies that are nonegalitarian in their hierarchical structure. Kelly assumes that simple egalitarian foraging societies are evolutionarily older than complex nonegalitarian societies.
Kelly agrees with Christopher Boehm that not everyone is really equal in egalitarian foraging societies (243-44). Some people have more wealth and status than others. And some people do exercise informal leadership over others. "There are people in every society who will try to lord it over others, but egalitarian societies contain ways to level individuals," so that ambitious people are punished for their arrogance, and thus everyone protects their individual autonomy. In large sedentary societies, however, sedentism releases the constraints of a nomadic foraging life and allows those with domineering personalities to express their natural desire for ruling over and dominating others (249). Kelly does not mention, however, Boehm's claim that modern liberal regimes can limit such domination and open access to power so as to revive the natural desire for individual autonomy expressed in small foraging societies, which confirms the Lockean and Smith argument for liberal social orders based on equal liberty.
Kelly concludes his book, in Chapter 10, by arguing that ethnographic studies of living foragers cannot be taken as providing any model for prehistoric foragers. But he qualifies this argument in a way that implicitly recognizes a universal human nature of foraging life. He writes:
"After the first edition of this book was published, a colleague asked me if there was anything from the ethnographic data that I thought could be projected into prehistory, something that we could assume in a model of the past. Then and now, I think there are only two things: nomadic foragers live in residential groups of somewhere between eighteen and thirty people, and men hunt while women gather. And I feel comfortable making those assumptions not because they are empirically common, which they are, but because we can provide a theoretical justification for each, as we have done in this book. A standard group size across environments results from the balancing of the desire to reduce daily variance in food intake while minimizing the rate of depletion of the foraging radius, and the division of labor is rooted in fundamental biological differences between men and women and the incompatibility of children with hunting. If we have correctly determined the causal conditions of these behaviors, and if we can assume those conditions were true of the past, then the assumptions are provisionally valid" (274).Doesn't this recognize--explicitly or implicitly--many of the traits of human biological nature as likely expressed in prehistoric foraging societies? Doesn't it point to the natural desires for food, for sexual identity as male or female, for parental care, for conjugal bonding, for social status, for justice as reciprocity (in the sharing of food), and for speech (in negotiating the terms of social life)?
If this is so, then recognizing the variability in hunter-gatherer societies is fully compatible with recognizing the regularities in these societies that manifest our evolved human nature.