If we observed another species evolve as dramatically as modern humans have over past many thousands of years, we would presume that the change was genetic—the natural selection of genetic variation must be involved. But this has not played a significant role in the evolution from hunters and gatherers to the modern culture. We know this because, over time, we see little or no change in human biology, including the capacities for culture. The evolution of irrigation agriculture did not require genes for irrigation agriculture. When modern hunters and gatherers emigrate to an industrial culture, they can adapt, and vice-versa.
The cause of the evolution from stone to bronze to iron and beyond—and thus the trajectory towards more, more and more—must therefore rest in the capacities for culture, as they evolved in our pre-cultural ancestors. Hence, if we can identify what has caused our capacities for culture to be put towards these ends, and understand the process by which culture evolves, we might also be able to ascertain whether we are able to control our future evolutionary trajectory.
That is the object of this book: to elaborate a theory of human cultural evolution. This theory builds on certain key concepts of anthropology and sociobiology, rejects others, and fills in gaps.
A theory of cultural evolution must carefully delineate the relationship among culture, human biology and natural selection. Criteria for such a theory include:
- Explain the general direction of cultural evolution, the long arc.
- Account for diversity among cultures.
- Describe the process by which culture evolves.
- These must be done while holding human biology constant.
- Explain how natural selection of genetic variation could give rise to the biological capacities for culture, yet does not appear to be significantly implicated in cultural evolution for the past many thousands of years.
I will add one additional criterion. A previous book, Dynastic Theory: The Evolution of Altruism in Animal Societies, set forth a theory of the biological evolution of group adaptations in all other species—including our pre-cultural, hominid ancestors. A key component of this theory is that animal societies are structured through natal philopatry—what I call dynastic structure. Members of an animal society are related by descent to a common founder of the society. Human societies are not structured dynastically. Although families are central to social structures in all societies, group bonds in large modern societies extend far beyond kinship. A theory of cultural evolution must explain why human societies are an exception to the rule in other animal societies.
The theory is called epigenetic evolution: a theory of cultural evolution through directed creativity. In brief, the theory holds that human minds create, select and build the “library” of culture, which exists above the level of individual humans. Because culture is communicated from minds to minds through language, culture evolves separate from the pathway of biological reproduction and inheritance—and, thus, is decoupled from natural selection. But as minds create, select and build culture, they are biased in a Darwinian direction. This is because, as the human brain evolved through natural selection in our pre-cultural ancestors, the psychology that motivates the brain to action co-evolved with it.
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