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| Nature Contents: 29 June 2000 Volume
405 No. 6790
Mosaic evolution of brain structure in mammals ROBERT A. BARTON
AND PAUL H. HARVEY http://www.nature.com/nlink/v405/n6790/abs/4051055a0_fs.html
The mammalian brain comprises a number of functionally distinct
systems. It might therefore be expected that naturalselection
on particular behavioural capacities would have caused size changes
selectively, in the systems mediating those capacities. It has
been claimed, however, that developmental constraints limited
such mosaic evolution, causing co-ordinated size change among
individual brain components. Here we analyse comparative data
to demonstrate that mosaic change has been an important factor
in brain structure evolution. First, the neocortex shows about
a fivefold difference in volume between primates and insectivores
even after accounting for its scaling relationship with the rest
of the brain. Second, brain structures with major anatomical and
functional links evolved together independently of evolutionary
change in other structures. This is true at the level of both
basic brain subdivisions and more fine-grained functional systems.
Hence, brain evolution in these groups involved complex relationships
among individual brain components. |
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