The latest in my ‘Learn Something New Every Day’ series… Taken from The Great Courses’ Trails of Evidence – How Forensic Science Works lecture series (Lecture 23 – Forensic Anthropology)
Most people believe that a woman’s pelvic girdle widens at sexual maturity to cope with childbirth but this is, apparently, an untruth. Or at least a partial untruth.
Other species females don’t change shape in preparation for birth, not even other primates – only humans. Turns out the wider pelvic girdle of a sexually mature female is caused by the giant head-to-body ratio of the human infant she’s going to have to squeeze out.
A baby’s skull is 75% its final adult size at birth, and while its body may be tiny and its bones malleable enough to squeeze through a birth canal without shattering, its noggin—even with the cracked ice-field of skull bones that later knits—is not. Female Homo sapiens have adapted pelvises to make sure that big clonker can get through without killing us.