Human Gestation Period- Why Is It What It Is?

I know this has been touched upon in other threads, but not this way. I was holding my 3 1/2 month old godson a few days ago, and this just kind of landed in my head. Now, I wanna know why.

Human babies seem to be amongst the most frail of newborns. They’ve got the rooting reflex down, so assuming that a lactating female is handy, they can eat- but only with assistance. Aside from that one truly innate reflex, they’re pretty much helpless. Witness preemies, with underdeveloped lungs, etc. Ever week in utero counts. counts.

Why is it that humans don’t develop more fully in utero?? I’m not trying to be facetious here. I want to know what it is that has determined that our species more or less delivers after 9 months of development, with so many senses not fully intact, etc. What development of our species made it desirable to have our offspring SO dependant upon us? Why not let us develop enough so that we were a bit more hardy? God knows life wasn’t cushy when we were living in caves and trees. Is it just so that the strongest infants survive? Survival of the fittest? Or, is there more to it?


Again evolution doesn’t do what is best. It does what works.

Many other animals are born helpless. Look at marsupials(sp?).

Many are born blind, while certain antelopes etc can run around in a day or less.

Larger brains, and the attendant larger skulls to accommodate them. Nature made the brain bigger, and the skull bigger, so mothers need to deliver the offspring at a point in development where the skull bones are a bit softer and not completely “set,” as it were.

The answer is, of course, evolution. Typically, infants born early will not survive, so the tendancy is for the gestation period to lenghten. Fourteen pound (10 month?) babies tend to have a tough time fitting throught the birth canal, thereby killing the mother (and themselves, as well).

IIRC the traditionally longer periods of gestation are associated with more “intelligent” animals who have a larger benefit from attaching a closer bond with Mummikins. Children learn language and most of what they need to know in the first few years of life; their brains remain plastic until well after age ten. Is this arguing a posteriori? Damn straight; see above comments on evolution.

Babies have several ingrained reflexes. Apart from the sucking reflex, their is the rooting reflex (rub cheek, babies head turns towards nipple or astimulus), planting reflex (prelimiary walking - baby will sort of walk if suspended above flat surface), grasp reflex (will squeeze hand or bottle), tonic-clonioc reflex, parachute reflex, Moro reflex (baby goes wiggy when frightened) and primitive brainstem reflexes. <ost of these diappear between 4-12 months; persisting reflexes are not about bragging rights on the annual Christmas card.