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Perhaps much of the controversy about evolutionary psychology devolves from forgetting some basic biological definitions. The gene is the unit of inheritance, which has a complex and imprecise relationship with the mature, viable organism that has inherited it. The unit of evolution is the individual organism. Therefore, the arguments about what is more important in evolution are specious. Since “survival of the fittest” is actually an ecological phenomenon that occurred in the distant past under conditions that cannot now be duplicated, we will never prove which genes mattered most then for any given species.

David P. Vernon
Tucson, Ariz.

Any system can evolve if it has some filter (environmental pressure) that selects some variants and not others, as well as some way of retaining the successful variants. As Charles Darwin’s contemporary William Bateson showed, sometimes the system and its environment coevolve, as in the case of horses and grasslands. Sometimes, both/and is better than either/or.

Roger M. Krause
Chicago, Ill.