The Birth Canal Is the Constraint

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Our brains can't really get any bigger because of the limitation of the skull passing through the pelvis opening in the female for birth. The relative growth rates of white and grey matter are such that our brains could not get bigger than about three times their present size a without basically collapsing an a number of other sort of constraintson you're quite right. In point of fact, if you look at a human from one perspective, we're absolutely monstrous, because we have these colossal heads. And n of course, as we grow into adult hood, the body gets bigger and the head gets proportionately smaller. We might get on to the conversation acause what our brain can do already is so phenomenal

If extraterrestrial intelligences exist, will look anything like us? Are we alone in the cosmos? If we reran the tape of life, would humans appear again? Is there purpose in the cosmos?

Shermer speaks with Cambridge evolutionary palaeobiologist Simon Conway Morris whose latest book challenges six assumptions that too often pass as unquestioned truths amongst the evolutionary orthodox. These include the idea that evolution is boundless in the kinds of biological systems it can produce. Not true, he says. The process is highly circumscribed and delimited. Nor is it random. This popular notion holds that evolution proceeds blindly, with no endgame. But Conway Morris suggests otherwise, pointing to evidence that the processes of evolution are “seeded with inevitabilities.”

Shermer and Morris also discuss: convergent evolution and directionality in evolution; chance, contingency, and law in evolution; theistic evolution and teleology in nature; why Morris is a Christian but rejects Intelligent Design creationism; free will and determinism; and whether there good arguments for God’s existence.