Incorporating culture into an expanded theory of evolution will provide the foundation for a universal account of human diversity. Two requirements must be met. The first is to see learning as an extension of the processes of evolution. The second is to understand that there are specific components of human culture, viz. higher order knowledge structures and social constructions, which give rise to culture as invented knowledge. These components, which are products of psychological processes and mechanisms, make human culture different from the forms of shared knowledge observed in other species. One serious difficulty for such an expanded theory is that social constructions may not add to the fitness of all humans exposed to them. This may be because human culture has existed for only a relatively short time in evolutionary terms. Or it may be that, as some maintain, adaptation is a limited, even a flawed, aspect of evolutionary theory.