The first thing that comes to my mind when I read Mike Hall's post is that from a sociological point of view, the structure of the family unit itself has drastically changed. The rise in the number of female-headed households is astounding, and families have already begun to "adapt" so to speak. I'm not certain if these adaptive methods qualify as actual PA's, per the great minds of EP, but as a sociologist, I see many changes occurring in mere survival of the family unit. Take economic survival today, vs. hunters/gatherers. It seems that the gender of the hunters have changed in order to feed their brood. Are women becoming stronger bread-winners, or were they always genetically programed to care for their children. The roles in our society have changed. We will, necessarily, need to adapt.
Also, look at China, and the population explosion. The government felt the need to step in to regulate the numbers of children being born. If you consider this in terms of our genetic heritage to breed and to survive, how does this change the role of women, not only in their role as breeders, but also in how they see themselves.
Finally, we are not just machines. As our species has grown and adapted over time, our intellect has had to adapt to incorporate, and utilize emotional input. This includes things like self-esteem (consider societal role changes of males and females), female and male aggressiveness in courtship (who does it benefit to do the pursuing), and how children of the future see their own adaptive roles, based on what they see occurring today (changes in what is today considered a family unit).
We may still have genetic encoding to see the family unit as headed by one adult male, and one adult female, with children resulting, but look at the statistics of what makes up a family in 1998. It does make you wonder.
Mary Beth