I think the idea of built-in variation within a population (not just across an individual's lifetime but between individuals) is fundamentally different though. It is an entirely different strategy and is flexible not only in the evolutionary long term but in short term stress on a population. You see it in plants for instance where variation within the species is used to allow for differences from one growing season to the next. The cost of course is that part of any given generation is going to be *mal*adapted to any given year.

More and more evidence seems to indicate that that is our normal pattern. And the idea of "natural" and "unnatural" I think is also unravelling as we find that many of our supposedly free choices are in fact genetically predisposed.