Naked Science Forum

Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: GlentoranMark on 21/12/2009 16:30:18

Title: Is left and right handedness unique to humans?
Post by: GlentoranMark on 21/12/2009 16:30:18

Are humans the only species that do most of their tasks using one side of their body?

Do Cats, Dogs, Monkeys ect?

Title: Re: Is left and right handedness unique to humans?
Post by: AllenG on 21/12/2009 23:26:48

According to Michael C. Corballis it seems to be a human characteristic. His theory is it developed as a consequence of the brain's anatomy and higher speech ability.

The strong predominance of right-handedness appears to be a uniquely human characteristic, whereas the left-cerebral dominance for vocalization occurs in many species, including frogs, birds, and mammals. Right-handedness may have arisen because of an association between manual gestures and vocalization in the evolution of language. I argue that language evolved from manual gestures, gradually incorporating vocal elements. The transition may be traced through changes in the function of Broca’s area. Its homologue in monkeys has nothing to do with vocal control, but contains the so-called “mirror neurons,” the code for both the production of manual reaching movements onto the perception of those same movements performed by others. This system is bilateral in monkeys, but predominantly left-hemispheric in humans, and in humans is involved with vocalization as well as manual actions. There is evidence that Broca’s area is enlarged on the left side in Homo habilis, suggesting that a link between gesture and vocalization may go back at least 2 million years, although other evidence suggests that speech may not have become fully autonomous until Homo sapiens appeared some 170,000 years ago, or perhaps even later. The removal of manual gesture as a necessary component of language may explain the rapid advance of technology, allowing late migrations of Homo sapiens from Africa to replace all other hominids in other parts of the world, including the Neanderthals in Europe and Homo erectus in Asia. Nevertheless, the long association of vocalization with manual gesture left us a legacy of right-handedness.

Source (http://www.bbsonline.org/documents/a/00/00/22/71/index.html)

Right and left symmetry is seen in other species, such as the shells of some species of mollusks like the conch being wound either clockwise or anti-clockwise. 

Title: Re: Is left and right handedness unique to humans?
Post by: GlentoranMark on 23/12/2009 09:30:10

Thanks, I was always curious.