Monday, August 15, 2005

Most Chimps Are Lefties

We humans show a distinct preference for our right hand. It is a big puzzle for scientists, as no other mammal showed a preference for their left or right limb. Till now that is. It seems chimpanzees, our closest relatives, show a preference for their left hand! Does it say something about our past perhaps? Perhaps when our ancestors split from theirs, ours split with a right-handedness, whereas their ancestors split with a left-handedness:-? It is a mystery:).

My other self:D (Courtesy: Strange Zoo)
A three-year study of 17 wild chimps in Gombe National Park, Tanzania, found that 12 of them used their left hands when using sticks to probe for termites. Four were right-handed and one was listed as ambiguously handed. The findings (by research team led by William D. Hopkins of the Yerkes National Primate Research Center at Emory University in Atlanta) are reported in Proceedings of the National Academy of Sciences.
The paper also looked at previous studies of chimpanzees and found that others had noted a left-handed preference when using sticks to fish for termites, but there had been reports of a right-handed preference when cracking nuts:)).
Because the hands are controlled by opposite sides of the brain, the finding could indicate that this brain division had begun as long as 5 million years ago, prior to the split between humans and chimpanzees:):).

15 comments:

  1. Cool! But why was this preference needed at all? Isnt a chimp/man who can use both hands fully, much better than ones that favour only one hand? Isnt it an evolutionary degradation?

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  2. Anyway, this chimp looks really cute! Next candidate for the profile photo?

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  3. Isnt it an evolutionary degradation?

    Actually, no. If you think about it, our two hands are not always needed exactly in the same way. If you are crushing nuts on a rock, you might use the left hand to hold the rock, and the right hand to bring down a stone to crush the nut. The requirements on the two hands are very different, and it makes sense to specialize.

    Abt. the chimp:), it was my desktop wallpaper for a long time. I just might select it for the profile too, it is very cute:).

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  4. It might work for the chimp-nut case. But look at human writing... If one of the arms were more dextrous and the other more powerful, then it could make some sense. But both dexterity and power in the same hand, and the other one always only for support. doesnt make an evolutionary superior to the other possibilities

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  5. True. But humans didnt evolve so that they could write! Perhaps in future, we can evolve away from this left-right asymmetry.

    Also, you have to keep in mind that evolution specialized the left and the right half of the brain, and our left or right-handedness might be connected to that. As long as being right-handed didnt prove to be a problem for ancient hominids, the specialization of the brain might have given them a distinct advantage, and the left/right-handedness just tagged along during evolution.

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  6. U mean to say that the right handedness was a side-effect of a more important shift in brain function, where the right-handedness didnt impact the survival/superiority, compared to the impact of the original shift of function.

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  7. I 'blogged about left handed some time ago.

    There's been all kinds of research into handedness over the years, and lefties like me have been persecuted throughout history for being so...

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  8. Sudhir: Yes :).

    Luke: Yup :D:D.

    Wayne: Minorities have always been persecuted throughout history. Pick any minority group based on any criterion :(.

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  9. I said in my post: no other mammal showed a preference for their left or right limb. Till now that is. It seems chimpanzees, our closest relatives, show a preference for their left hand :).

    BTW, chimps are apes (like us humans) and not monkeys. Chimps have no tail, they have oppposing thumb and a big brain (compared to monkeys) like us :).

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  10. As I am left-handed, I must not have completely evolved. This may explain a few things...

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  11. Ahan, perhaps u evolved like the chimps, who are mostly left-handed too =))... dont worry, you are in good company, urs truly is mostly left-handed as well :-$.

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  12. C'mon...we all know what the left hand is used for :D :D :D

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  13. cute pic:)
    interesting too. though i suprised it took so long for this point to be noted.
    if i am chimps evolved from monkeys, what about monkeys , are they right handed or lefthanded?

    PS: I do get irritated when children who use the left hand are discouraged.

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