Chapter 8, The Fitness of Human Nature

This is perhaps the core chapter of the book, in that it brings together ideas about the mind, genes, and culture from the previous two chapters, and sets up a basis for the examination of several aspects of human culture in the subsequent chapters.

Key points in this chapter:

  • Human nature is “the hereditary regularities of mental development that bias cultural evolution in one direction as opposed to another…”
  • This is not genetic determinism;
  • Examples of some of these regularities include kin selection and altruism; parental investment; differing mating strategies of men and women; status; territorial expansion and defense; and contractual agreement.
  • A particular example that illustrates these principles is incest avoidance.
  • With my comments (at the end) about the attraction of these ideas and their relationship to science fiction.

Summary and Quotes:

What is human nature? Not genes or culture. Rather

human nature is something else for which we have only begun to find ready expression. It is the epigenetic rules, the hereditary regularities of mental development that bias cultural evolution in one direction as opposed to another, and thus connect the genes to culture.

He summarizes epigentic rules mentioned so far, from fear of snakes to naming of colors. He resolved the apparent paradox that “culture arises from human action, [and] human action arises from culture.” Then he addresses how he anticipates some will take these ideas, p166.8:

The general biological imagery of the origin of human nature has repelled some writers, including a few of the most discerning scholars in the social sciences the humanities. They are, I am sure, mistaken. They misunderstand gene-culture coevolution, confusing it with rigid genetic determinism, the discredited idea that genes dictate particular forms of culture.

Genetic evolution might have done it differently… But we’ve never seen an example of bias-free mental development. Our epigenetic rules remain in place, despite recent rapid cultural evolution. Genes from the Upper Paleolithic, from 40,000 to 10,000 years ago, remain today.

Thus sociobiology (aka or Darwinian anthropology, or evolutionary psychology) poses certain questions and has identified some basic categories of evolutionary principles, described with a couple paragraphs each beginning 168b. (Many are familiar from Pinker; of course).

  • Kin selection. Which led to altruistic behavior.
  • Parental investment: behavior toward offspring that limits parent’s ability to invest in further offspring.
  • Mating strategy: how women have more at stake in sexual activity than men.
  • Status.
  • Territorial expansion and defense. Another cultural universal… “Our country right or wrong.” Not present in some other species. In humans it arises from competition for vital resources.
  • Contractual agreement: we take it for granted, because it’s everywhere; it entails cheater detection as a corrective to altruistic behavior.

The genetic fitness hypothesis has been reasonably well borne out by the evidence. People live as if guided by these principles. There remain some weakness, mostly due to scarcity of data. The shortcomings are ultimately solvable. The human behavior that is the best example is incest avoidance. It’s near universal and can be explained straightforwardly. We understand the risk of defective children from incest. (Details.) Many plants and animals use some method to avoid incest. Exogamy is one, 174m. Sometimes males, sometimes females. And, adults spurn others with whom they were close early in life. This was discovered in 1891; later confirmed by a large study in Taiwan, and later in Israeli kibbutzim. This is called the Westermarck effect. Still, we don’t conclusively know that this is due to genetics. Nor do we know the psychological trigger. Meanwhile, incest taboos *are* cultural. Yet they vary considerably among cultures. And there are exceptions. There’s one other hypothesis aside from the Westermarck effect: Freud’s, who thought taboos prevent irresistible lust among family members, including the Oedipus complex. James Frazer felt the taboo would be unnecessary if the Westermarck effect existed. This view prevailed for most of the 20th century. Freud resisted the Westermarck idea because that would show that he was wrong in general, 179t. So is morality a convention from mode and custom? Or derived from innate emotions? Currently, the evidence leans toward Westermarck. Further, consequences of incest can be seen directly. With various folk theories invested to explain them. The summary is that incest avoidance comes from multiple, successive barriers. Desensitation among kin; dispersal of young; cultural taboos. Does this mean humans made the last a rational choice? Not really…



I’ve been fascinated by ideas like these ever since I first read Wilson’s ON HUMAN NATURE back in 1978 (my review of 2019 reread here) because they bring into focus ideas that most people, if they thought about them at all, would think are necessarily or self-evidently true (e.g. status, territorial expansion). When in fact other animal species have different, often quite different, default genetically-installed strategies of their own. It’s a sort of failure of imagination among people to think that humans are default normal and typical.

Which is where science fiction chimes in! Would aliens, intelligent species like our own, have similar natures? To speculate properly, you’d have to propose differences in the evolutionary background of such aliens compared to ourselves, or perhaps fundamental differences in environments, and deduce how and why alien temperaments might be different from our own. For example, species who give birth to broods, or litters, rather than single children (as do humans most of the time), would have very different strategies for raising children; there wouldn’t be the same kind of sibling rivalry, or parental preferences (humans tend to grieve the deaths of older children more than younger). I don’t recall, off hand, any SF stories that have engaged in this kind of analysis; most SF aliens simply exaggerate some tendency of humans.

An exception might be James Tiptree, Jr. (a female writer with a male pen-name). She did exogamy in her short story “And I Awoke and Found Me Here on the Cold Hill’s Side,” in which humans chase the irresistible exoticism of alien tourists to Earth. (IIRC) Aliens tweaked with human hormones to exaggerate the male sexual drive, in “The Screwfly Solution” — to bring about humanity’s destruction. And “Love Is the Plan, the Plan Is Death” depicts the bizarre lifecycle of an alien species (I read it so long ago I don’t remember the details).

Another possible exception: Ursula K. Le Guin, who especially back in the 1990s, wrote a series of novelettes and novellas depicting alternative social and sexual arrangements among alien, or human-derived, cultures on other planets. Haven’t read them since them, but I’m curious to revisit them and see if those arrangements made sense given circumstances… or if the stories were designed simply to challenge conventional (human) thinking.

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