William Durham:
"Coevolution" (Stanford University Press, 1991)

(Copyright © 2011 Piero Scaruffi | Legal restrictions - Termini d'uso )
William Durham's book begins with a lengthy examination of previous theories of cultural evolution, which is basically an introduction to Evolutionary Anthropology.

But first Durham goes out of his way to distinguish culture from behavior. Culture is a system of rules for behavior, but it is not the only system that determines behavior: genes and the environment being other ones. Culture is not a set of behavior patterns but a set of control mechanisms that determine behavior patterns.

Culture is learned information that is conveyed socially and symbolic in nature (as in "language"), that has evolved over time, and that comes to constitute a system of knowledg ("every culture is a structure", as Clyde Kluckhohn emphasized in 1960)

All of this sounds very unscientific to people from information science in which there are clearcut definitions for symbol, information and knowledge, as do pretty much all the definitions in this book.

He classifies theories of Evolutionary Anthropology in three categories, depending on whether they consider culture a separate system of inheritance and what kind of units of inheritance they assume: models without dual inheritance (that do not recognize cultural evolution as a separate system of inheritance but simply as a product of genetic evolution), such as Sociobiology; models with dual inheritance (in which cultural evolution is a separate system of inheritance) whose units of inheritance are patterns of behavior (Richard Alexander's "social learning model", Luigi Cavalli-Sforza's and Marcus Feldman's cultural transmission model, Charles Lumsden's and Edward Wilson's gene-culture transmission model, whose unit is the "culturgen" which is subjected to "epigenetic rules"); and models with dual inheritance whose units of inheritance are memes (Albert Keller's "social selection model" whose units are "mental changes", Ronald Pulliam's and Christopher Dunford's "programmed learning model" whose units are "ideas", Robert Boyd's and Peter Richerson's "Darwinian model" that emphasizes the different "parental" status of cultural transmission and genetic transmission). ).

Durham sides with the third category, according to which human behavior is determined by two main information systems, one genetic and one cultural, that both spread over time and space. In other words, both the genetic repertory (the genotype) and culture are information systems that instuct phenotypes. The genotype and culture stand in a symmetrical relationship to the environment, in that the environment selects "what" gets transmitted (inherited) in space and time. So genotype and culture stand in a symmetrical relationship with both the phenotype (each of them "instructs" it, although in different ways) and with the environment (each of them is "selected" but it, although in different ways).

Before adopting Dawkins' term "meme", Durham refers to the "ideational theory of culture" (a confusing term coined by Roger Keesing in 1974), in which ideational phenomena are things like values, ideas and beliefs, none of which gets defined properly and therefore simply sounds amateurish. After adopting the term "meme", Durham introduces the concepts of "holomeme" (any variant of a meme) and "allomeme" (any variant that results in behavior).

Durham believes that cultural evolution is due to two fundamental processes: transformation and diversification of cultures. Diversification is the by-product of isolation. Transformation is the product of interaction with the environment.

Finally, Durham advances the theory that two main forces are responsible for spreading culture across space and time (this is vague too, as he can't help adding "the main but not exclusive"): "selection by choice" and "selection by imposition". Choice is unique to culture because parents cannot choose which genes to pass on to their children, nor can children choose which genes to accept, whereas cultural parents can choose what to pass on and cultural children can choose what to accept. Imposition arises from the intervention of an intermediary that does not exist in the case of genetic transmission: sociopolitical constraints. Durham thinks that the latter is the main factor of cultural evolution: decision makers decide, to a large extent, how culture evolves. In a sense, cultural evolution exhibits another unique property: self-selection. The cultural system can influence the direction and rate of its own evolution: memes influence decisions that influence memes. The cultural fitness of an allomeme indirectly depends on the meme itself too.

His theory also envisions five different modes of interaction between cultural and genetic evolution that he calls respectively: "genetic mediation" and "cultural mediation", which constitute coevolution in the narrow sense (in which each one acts as a selecting environment on the other one), plus "enhancement", "neutrality" and "opposition", which constitute the effect of decision making, i.e. of self-selection.

By the end of the book, one is almost convinced that genetic evolution and cultural evolution have little in common.

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