Saturday, February 16, 2008

Heads or tails

One last comment before I put away Tim Birkhead's book. Consider this tidbit of information: Male fruit flies of the species Drosophilia bifurca produce sperm that are 38 times as long as their bodies. That is, the fly is about as big as this letter i, and its sperm is as long as your little finger. It's as if a human male produced sperm as long as a football field. Producing such sperm and delivering them successfully to a female takes some doing, as you can well imagine.

And what do intelligent design advocates make of such a fact? One can only imagine the Creator sitting as His drawing board chuckling to Himself as he imagines yet another bit of whimsy.

Evolutionists, at least, can suppose that long sperm -- which females seem to prefer -- confer some adaptive advantage. For example, does the pinkie-long tail provide nourishment to the fertilized egg? Well, let's do the observations. Nope, only the gene-bearing head of the sperm is absorbed by the egg. Do long tails let sperm swim faster? Nope, the longer tail produces greater propulsive force, but this is more than offset by greater drag. There are at least a half-dozen other hypotheses, including the possibility that big sperm in fruit flies are like a big rack of antlers on a stag; they signal reproductive fitness in the male. As far as I know, the issue hasn't been resolved -- which is nice, because it means more work for biologists. The intelligent designists, on the other hand, can rest on their laurels; their work is done.