Re: Shrinking brains in evolution

On May 13, 10:08 am, dkomo <dkomo...@xxxxxxxxxxx> wrote:
In _Evolving Brains_, John Allman mentions that early modern humans had
brains that averaged 1450 grams, whereas the average for contemporary
humans is about 1300 grams. He opines that this is a result of the
"domestication" of humans. The development of agriculture and
domestication of animals as sources of food and clothing have served as
major buffers against environmental variability.

Reduction in brain size and neuron number have been observed in many
domestic animals relative to their wild counterparts. Dogs have brains
that are about three quarters the size of the brains of wolves of
comparable body size. Humans have assumed the responsibility for
providing food and shelter for dogs, and thus the dog's necessity for
maintaining a larger brain is decreased. Large brains are also very
energy intensive, and so there is a selective advantage in making them
smaller.

Another example comes from the comparison of the retinas of European
wild cats and domestic cats. Domestic cats have 40% fewer retinal
ganglion cells, which relay the input of the retinas to the brain. This
major loss of neurons might be produced by programmed cell death in
development and linked to domestication.

--dk...@xxxxxxxx

It seems to me that modern computers are both much more powerful
and much smaller than computers in the 1960s. More efficient design.

Evolution does not "design" except if we use the word
figuratively, but accomplished the same result. Besides the fact that
the brain is a greedy organ (i.e. consumes 26% of your oxygen and 29%
of your glucose), humans have immense difficulties with childbirth
compared to other animals due to the large size of the baby's head.
Clearly there would have been strong evolutionary pressure to evolve
brains as good or better that were smaller. It would be foolish to
suppose that there is any linear correlation between brain size and
intelligence, particular when we compare ancient and modern human
specimens.

.

Relevant Pages

  • Re: Shrinking brains in evolution
    ... brains that averaged 1450 grams, ... humans is about 1300 grams. ... domestication of animals as sources of food and clothing have served as ... Domestic cats have 40% fewer retinal ...
    (sci.bio.evolution)
  • Re: Shrinking brains in evolution
    ... brains that averaged 1450 grams, ... humans is about 1300 grams. ... domestication of animals as sources of food and clothing have served as ... Domestic cats have 40% fewer retinal ...
    (talk.origins)
  • Re: Shrinking brains in evolution
    ... brains that averaged 1450 grams, ... humans is about 1300 grams. ... domestication of animals as sources of food and clothing have served as ... Domestic cats have 40% fewer retinal ...
    (sci.bio.evolution)
  • Re: Shrinking brains in evolution
    ... brains that averaged 1450 grams, ... humans is about 1300 grams. ... domestication of animals as sources of food and clothing have served as ... Domestic cats have 40% fewer retinal ...
    (sci.bio.evolution)
  • Shrinking brains in evolution
    ... In _Evolving Brains_, John Allman mentions that early modern humans had brains that averaged 1450 grams, whereas the average for contemporary humans is about 1300 grams. ... The development of agriculture and domestication of animals as sources of food and clothing have served as major buffers against environmental variability. ... Domestic cats have 40% fewer retinal ganglion cells, which relay the input of the retinas to the brain. ...
    (talk.origins)