birth canal & soft spots

alex duncan (
9 Aug 1995 19:44:03 GMT

In article <> Bryce Platt, writes:

>Given that other animals have these soft spots, and that moulding of the
>cranium does take place (my 4-week old granddaughter is still something of a
>conehead), what explanations do we have for the smallness of the human birth
>canal in relation to cranial size? My wife the obstetrics nurse says that all
>the other parts can bend and twist adequately, it's just the head that is the

The small size of the human birth canal is imposed by the constraints of
bipedal locomotion.

Please note that I wasn't saying soft spots don't come in mighty handy
during delivery of human infants. They do. Its simply a mistaken step
to note that the unfused cranial bones are an aid to delivery, and to
then claim that is why the cranial bones are unfused.

Alex Duncan
Dept. of Anthropology
University of Texas at Austin
Austin, TX 78712-1086