Well, this New York Times column expertly deflates that claim vis-a-vis depression. Besides presenting evidence that the ruminating thought style of depression is of little advantage if any, it notes that ... cancer has zero evolutionary advantage.
Even if depression is “natural” and evolved from an emotional state that might once have given us some advantage, that doesn’t make it any more desirable than other maladies. Nature offers us cancer, infections and heart disease, which we happily avoid and do our best to treat. Depression is no different.Game, set, match.
Meanwhile, the more we learn about epigenetics, the more we realize that, not only does it TOTALLY upset the Pop Ev Psych applecart, it's even leading more and more biologists to consider "Lamarckianism lite" as a valid extension on traditional evolutionary biology.
But with the skyrocketing prevalence of conditions such as obesity, diabetes, and autism, which have no clear genetic etiology in the majority of cases, as Brunet pointed out, “It seems that all complex processes are affected by epigenetics.”A whole new ballgame, in this case, to extend the metaphor.