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Re: Regularities in brain evolution?
SHICKLEY@VM.TEMPLE.EDU
Wed, 23 Aug 95 11:24:03 EDT
In article <41e6lb$c0r@newsbf02.news.aol.com>
kathiedon@aol.com (KathieDon) writes:
>
> Hello. I'm an "amateur" paleoanthropologist with an interest in brain
>evolution, esp. human brain evolution. In Science (16 June 1995), Finlay
>and Darlington propose a model of brain growth across mammals. They
>suggest that the size of any one brain feature correlates more stongly
>with overall brain size than with any other feature of the organism. A
>suggestion here, then, is that the brain expands as a whole, not
>piece-meal. Therefore, I speculate, no one feature of the human brain
>(large neocortex, large cerebellum, large limbic system) needs
>explanation--what needs explanation is why the entire brain expanded.
> I think that something of a "decoupling hypothesis" is called for
>here. The decoupling was brain growth from body growth. Under this
>picture, a mutation or, more probably, linked series of mutations resulted
>in "runaway brain growth," which in turn permitted new functions (i.e.
>behaviors and mental processes), which proved to be adaptive in the
>environment at that time. I would tentatively use this idea to explain
>the divergence of early Homo from Australopithecus, and possibly also the
>divergence of Homo sapiens from Homo erectus.
> I'd appreciate any comments on this approach to thinking about brain
>evolution. For personal replies, please send messages to:
> scs8403@ocvaxa.cc.oberlin.edu
> Thanks,
>
> Carl Sachs
>
>
>
>
Coupled with an increase in brain size and head size must have been an
accomodating change in the pelvic arrangement in order to give birth
to a larger-headed offspring. While there is a great deal of postnatal
growth of the head and brain, a significant change in size would require
the pelvis to be able to permit passage. There is some concern in the
medical community now that the rampant use of caesarian surgery for
birth is creating a selective pressure for smaller (inadequite)
birth canals.
Tim Shickley (shickley@vm.temple.edu)
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