 While it seems that the accusation that the early “Pop” sociobiologists were genetic determinists was probably unfair, there is a related objection that can be raised to both “Pop” sociobiology and to the later forms of human and non-human behavioral ecology, i.e. that any trait’s being an adaptation requires that that trait be heritable, and most human behaviors are not heritable. To say a trait is heritable in the simplest sense is just to say that if the parent has that trait, then the trait tends also to appear in the offspring (i.e. to say the trait is heritable simply means that the trait is inherited reliably). The more demanding population genetic definition of heritability is that a heritable trait T is one where variation in T can be accounted for primarily by variation in genes as opposed to variation in the environment (see also the entry on  heritability).  Heritability in this sense is supposed to be required for natural selection because in order for natural selection to spread a variant T in a population, when T increases the average number of offspring of its possessors, those offspring have to reliably also have T if T is to spread at the expense of the other variants. The problem, however, is that many human behavioral traits do not seem likely to be heritable in this way: they tend to vary greatly across and even within cultures and environments, whereas human genetic variation is much too low to account for such differences (Buller, 2005; Cosmides and Tooby, 1987).