Tuesday, July 28, 2009

Evolutionary Thoughts on Left Handedness

So I found this article on Gene Expression and found a thought provoking discussion on this subject of left handednes... Check it out here

From the article:

Somewhere along our evolutionary history ... we departed from chimps and other apes to develop a gene for right-handedness (he called it D, for dextral). This was allied to the development of language, which happened in only one half of the brain — the left hemisphere. McManus, who is right-handed but whose mother was left-handed, explains: “It would not have worked to put language in both hemispheres, because the corpus collosum (the bundle of nerve fibres connecting the two halves) is relatively slow and inefficient. The connections within each hemisphere are fast and reliable, which is essential for language.

“In CD brains, instead of having language in the left hemisphere only and non-language things in the right hemisphere, some of those faculties flip over to the other side,” McManus says. “You get things side by side that you wouldn’t find in a right-handed brain; they are built in a different way which I think makes them advantageous.

“Imagine, for example, having spatial faculties in the left hemisphere — this means that symbols and language are next to each other. This is particularly good for doing mathematics. Although we are not sure, the proportion of left-handed mathematicians could be as high as 20 per cent; there is certainly enough evidence to believe that left-handedness and mathematical talent may be linked.”

However, having too much crossover between brain hemispheres — caused by a CC inheritance — may lead to “higgledy-piggledy brains”, according to McManus. This genetic combination may lie at the heart of why autism, dyslexia and speech disorders such as stuttering are overrepresented in the left-handed population (the conditions are also much more common among boys).

what is super interesting is the disproportionate amount of (genius/mental disabilities) represented in left handers. Apparently many savants are left handed... according to this Wired article on 'The Key to Genius'

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