Apologies for the lack of clarity. When I said 20,000 protein-coding genes are not enough, I was referring specifically to the traditional view that one gene c

Apologies for the lack of clarity. When I said 20,000 protein-coding genes are not enough, I was referring specifically to the traditional view that one gene codes for one protein. It's pretty well understood now that this is not the case, and my point was moreso that 20,000 genes in and of themselves fail to code for every different trait/behavior in a reductive model. I think epigenetics provides the powerful toolbox to illuminating on the unlimited # of interactions/permutations of genes that you describe. But what I find most fascinating about epigenetics is its ability to explain environmental vs biological effects on our traits/behavior, not intrinsically described by our genes. As the DNA-methylation described in epigenetics determines which genes are on/off, it is external stimuli that often affect the methylation of epigenetics in the first place. (a Nature brief on the topic in mice: http://njc.rockefeller.edu/PDF_BN08/topic%202-FrancisEpigeneticNature%20Neurosci.pdf http://njc.rockefeller.edu/PDF_BN08/topic%202-FrancisEpigene...) It's a fascinating way of understanding how our environment affects us on a biological level.