In the latest issue of Trends in Cognitive Sciences, Kovas and Plomin has an article about the implications of "generalist genes", should the theory be correct. The "generalist genes hypothesis" states that the same genes affect most cognitive abilities and disabilities. That is, our diverse cognitive apparatus — from language, to working memory, to visual attention — is affected by a few genes alone. This thought runs straight counter to the idea that genes can be responsible for one cognitive function alone.
Kovas and Plomin speculate about the meaning of generalist genes for our theories of how the brain works. From the article:
One possibility is that a generalist gene affects a single brain area or function that in turn influences several cognitive processes. The effect of such a gene would be general at the cognitive level, but specific at the level of localization in the brain. In other words, the structures and functions of the brain are uncorrelated genetically because they are influenced by different genes. We consider that this possibility is unlikely because pleiotropy suggests that any gene is likely to be expressed in more than one structure or function.
A second possibility is that cognition-related generalist genes pleiotropically affect multiple brain structures and functions, but each of these structures and functions affects a specific cognitive process. In other words, the structure and function of these specialized areas are correlated genetically because the same genetic polymorphism affects these different regions. Even though each brain structure and function is associated with one specific cognitive process, these cognitive processes are correlated genetically because the brain processes are correlated genetically.
The most likely possibility in our opinion is that generalist genes affect multiple brain structures and functions, each of which affects multiple cognitive processes. This mechanism would lead to genetic correlations both in the brain and in the mind.
I assume that generalist genes is initially incompatible with the thought of massive modularity as we see in evolutionary psychology. That does not rule out, however, the possibility of incorporating generalist gene'ism with EP. Yes, we can say that cognitive functions have evolved separately, but they might still be built out of the same genetic foundation. No need for logical inconsistency, as far as I can see.