Teleonomy and the Why of the Y

I was reading Dan Dennett's Breaking the Spell: Religion as a Natural Phenomenon this weekend and came across his use of the phrase free-floating rationale to describe the automatic discovery of solutions to fitness problems using evolutionary search. I think Norbert Wiener coined the term "teleonomy" to describe the same phenomenon. Dennett is very much up on the topic, so I'm surprised that he didn't cross-reference Wiener's rather nice term?

In related matters, Dennett references the notion that parasitism may be the driver for sex, originating with John Maynard Smith in "parental investment theory." The problem is that mixing one's genes together with another's needs explanation: why is sexual recombination apparently better than asexual? After all, in the latter the genes are faithfully copied without the threat of being coupled with some broken alleles that could lead to the end of the genetic lineage. The genetic mixing might be most important for immune response in (part of) Smith's reasoning, and the variability of immune response may be adequate to offset the costs of mixing.

Interesting, but there is another oddity. In mammalian males, our 23rd chromosome doesn't have backups for broken alleles (the "Y" chromosome). It turns out that my foster father asked the "why" question in the early 90s concerning Y chromosomes. The Why of the Y? Without a backup, genetic defects will build-up faster in males than in females. These "sex linked defects" reduce the robustness of males in comparison to females and, when combined with agressiveness and the physiological consequences of the hormones that drive aggressiveness, result in short, angry lives. So my foster father reasoned that the Y is a mechanism for increasing the exposure of defects under competition, driving deleterious mutations out of the population at a faster rate than if males did not have a Y. This is somewhat controversial, to say the least, because it suggests a meta-evolutionary or group selection-like mechanism, but it does provide a Why for the Y where few have asked the question before.