One of the penalties of walking on two
feet as opposed to the usual mammalian four is the size of the pelvis.
With
body weight and locomotion focused in the middle of the body the birth canal
tended to be reduced. An alternative was that Homo sapiens developed a
duck-like waddle as did earlier hominins such as Australopithecus. Humans want
to be elegant. The gorillas took the Soviet tank approach and Homo sapiens
in order to avoid being cat-food, reckoned that being fleet of foot was a good
thing as well as standing upright to observe and avoid danger on the savannah.
By contrast Homo heidleburgensis, an immediate
forerunner of H sapiens was tall and built very robustly both in jaw and muscle
attachments hence a real tough guy.
But back to the point; with the small pelvis, giving birth was not easy for the more graceful human ape. Remembering
that natural selection filters out the losers in evolutionary change the only
successful breeding mothers were those favoured with giving birth to immature
young. The consequence was that humans require infinitely more assistance to be
nurtured from a state of complete helplessness and still require help to
survive for the first ten or so years.
The upshot of these compromises
including large brain and less brawn and the need to be born small was that H
sapiens used intelligence to hunt for meat and kept out of danger whilst
the mothers bonded emotionally with their helpless offspring for an extended period, allowing for a family
and social sense to develop in the child.
Behold: the modern human! Being so
recent however, around only two hundred thousand years, it seems to me we still
have a long way to sort out the nature of the human animal and put aggression
behind us.
Why are we still here? Because we have flexible thinking which employs imagination to project a future so we can make strategies. Our imagination makes us human but also subjects us to the weakness of assuming our imagination represents truth.