Hey folks, Can we stop with the anthro-centric evolutionary arguments? Please look at this image [1]: http://upload.wikimedia.org/wikipedia/commons/5/5b/Evolution_pl.png Five digits is clearly NOT optimal for some of these mammals. The mole needs more, the anteater and horse need fewer. Any argument that is based on just one function, like grasping a tool, is missing a lot of the issues. I suggest that we are limited to 5 fingers only because the common ancestor had 5, and it might have been stuck with something inherited from earlier in the synapsid[2] or general reptile lineage. - Robert [1] apparently from http://ncse.com/image/homologous-limbs -- a popular image; a different but equivalent image is at http://www.zoology.ubc.ca/~bio336/Bio336/Lectures/Lecture5/Overheads.html [2] bridge between reptiles and mammals, see http://en.wikipedia.org/wiki/Synapsid On Mon, Dec 20, 2010 at 12:48, Henry Baker <hbaker1@pipeline.com> wrote:
Re: redundancy
True, but then why not have 6,7 or 8? There must be a steep marginal cost associated with having 1 more finger, so that evolution calls a halt to digit inflation.
According to some theories, every square inch of skin is mapped to a distinct area of the brain, [...]
12/20/2010, Torgerson, Mark D wrote:
Maybe the issue is about redundancy. [...]
So maybe the question isn't "Is X digits optimal for the tasks at hand?" But rather "How far off from optimal is X-1 or X-2?" [...]
-----Original Message----- From: Henry Baker
I keep asking my friends in the evo-devo (evolutionary development) community why 5-fingered hands and 5-toed feet in humans are so resistant to variation -- particularly relative to the variation found in many other traits. [...]
There must be some extremely important tasks for which are impossible with only 4 digits/hand, as well as other extremely important tasks which are impossible with more than 5 digits/hand. [...]
At 09:33 AM 12/19/2010, Fred lunnon wrote:
Jon Selig tells me that the theory is familiar among the robotics community, having been developed 20+ years ago in the somewhat different context of the number of fingers required by a mechanical hand --- imagine trying to grasp securely a light, slippery ball, without it touching the palm. With one hand --- could be a good game for party forfeits in there!
The reference he gives is B. Mishra, J. T. Schwartz and M. Sharir, "On the existence and synthesis of multifinger positive grips", Algorithmica, Volume 2, Numbers 4, 541-558 (1987)
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