The December 11 issue of The Economist magazine carried an article
about lefthandedness.  It suggested that the fact that the left side of
the brain controls the right side of the body, and vice versa arose
because "long ago in the evolutionary past, an ancestor of humans (and
all other vertebrate animals) underwent a contortion that twisted its
head around 180 degrees relative to its body."

I am intrigued by this claim, which I have never heard before.  Could
someone offer more details about it?  What empirical evidence is there
for it? What do biologists suggest could have been the reason for this
"contortion" or was it purely an accident? Is it possible that it never
really took place, that there is actually some advantage to having this
left-right crossover in the brain?

I would be grateful if you could direct me to any good sources
understandable to a layman regarding this phenomenon. Thank you.
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 * RgateImp.MoonDog.BBS at 12/17/04 9:43:46 PM