IUBio

Size of brain and size of skull

Ian at dragoncon.netdeletethis Ian at dragoncon.netdeletethis
Sun May 30 00:56:16 EST 1999


On 28 May 1999 12:56:40 GMT, didier at Glue.umd.edu (Didier A. Depireux)
wrote:

>Ian at dragoncon.netdeletethis wrote:
>: On 27 May 1999 15:17:23 GMT, didier at Glue.umd.edu (Didier A. Depireux)
>
>: I think the limitation is the size of the birth canal. Its pointless
>: having a larger brain if you die during birth, probably killing your
>: mother in the process. How surgical techniques will influence this in
>: the future will be interesting.
>
>I agree with that, but that's not what I meant. The mother's pelvis only
>determines the brain size at birth, but you still have quite a ways to go
>between the size of your head at birth and the adult size. What I find
>surprising is that bone growth (the calvarium) should be _regulated_ in any
>way by the growth of a soft tissue like the brain. 
>
>						Didier

If I remember correctly the skull is not only pliant at a young age,
but there is a gap at the top of the skull. This is only slowly filled
in over time, I don't know how quickly. But possibly this does allow
the brain to have some determinism, some room to manoeuver. 

However, I suspect that both the skull and brain size are
predetermined by genetics to be a neat fit. As you know the brain
doesn't completely fill the cranial cavity, and even the surrounding
fluid is at relatively low pressure. I would have thought that if one
or the other was the restrictive factor then the space would be
completely filled.

Ian




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