Ayale published at Biologos another speculations. One of his attacks against ID was this emotive one (”On Reading the Cell’s Signature” Jan 7):
“The birth canal is too narrow for the head of the newborn to pass easily through it, so that millions of innocent babies—and their mothers—have died in childbirth throughout human history.”
I noticed darwinists that in fact this argument refutes Natural selection more than anything else. Because natural selection should have given advantage to woman with wider canals. Actually it was professor Adolf Portmann who mentioned this argument against natural selection.
Barb follows up:
This is very silly. For many years prior to germ theory, doctors would perform autopsies before delivering babies. Doesn’t Ayala think that contributed to the statistics for death of mothers and babies in childbirth, or does he ignore it in view of the fact that it doesn’t direct support evolutionary theory?
Part of the problem, here, is that advocates of ID and creationism simply do not understand evolution or natural selection.
In terms of human evolution, pelvic size and shape has changed as human brain size has increased. However, at some point increasing pelvic width interferes with bipedal locomotion so there is a tradeoff between them. There is a third factor in the equation. This is birth weight and natural selection has acted on that as well. See this series of studies for examples of how selection has acted to restrict birth weights to a narrow range – there is a trade off there as well. The gist of that series is that stabilizing selection has acted to restrict birth weight to a narrow range. The point of this, admittedly brief, post is that natural selection isn’t necessarily restricted to increases or decreases in the size of a given trait – indeed sometimes such linear increases aren’t actually the solution to the problem.