Recent discoveries in genetics are turning this bad gene vs. good gene model on its head and pointing toward what looks a lot more like the concept of intensifiers. Psychologists call it the “differential susceptibility hypothesis.” The same genes that lead to bad stuff can actually lead to great stuff in a different situation.

Too often, causation in biology, as indeed in the world in general, has been assumed to start “at the bottom” and filter up—so that, for instance, characteristics at the level of an organism’s traits are deemed to be “caused” by genes. As we’ll see, we can gain a better understanding of how life works, and how to intervene in it effectively, when w