Re: “hands free” births for humans
Cephalo-pelvic disproportion. A side effect of the human pelvis evolving that way to make upright walking feasible.
The average woman’s birth canal is roughly 2.5 cm narrower than the average with of a newborn’s head. Smooth passage through the birth canal is not an option. The passage is only possible because a newborn’s head is somewhat compressible because the skull bones have not fused into a single plate yet.
I am overly simplifying this, but the whole thing really works only because human babies are totally underdeveloped compared to any other mammal. Those are more or less fully developed mini-versions of their parents. They still have to grow and learn, but already can do all the basic stuff they need to survive from day one.
To paraphrase my mum: if men had to give birth, sex ed, contraception, abortions, etc would never have been controversial issues, anywhere, ever.
To paraphrase Bill Bryson: if there ever was anything to challenge the concept of “Intelligent Design” it is human childbirth.
