Human symmetry

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Ruairi
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Human symmetry

Post by Ruairi » Thu Jan 31, 2008 11:58 pm

Bilateral symmetry, being so widespread in nature, does not seem strange to me. But the (almost exact) correspondence of human arm span to height for some reason seems strange, perhaps because a) there is no obvious plane of reflection, that I can perceive and b) there is no clear aesthetic value, as there is with bilateral symmetry. Is is controlled by DNA or evolution? Why does it occur?

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Post by mcar » Fri Feb 01, 2008 1:07 am

Do you mean, the taller, the longer the arms?
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MichaelXY
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Post by MichaelXY » Fri Feb 01, 2008 3:22 am

I am thinking both. The DNA sets the arms lengths. But Evolution determined optimal arm length.

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Post by MrMistery » Fri Feb 01, 2008 8:42 am

there is a gene that directs the production of an enzyme that makes growth hormone. It is growth hormone that directs both your hight and the length of arms and legs.
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Post by mcar » Sat Feb 02, 2008 11:03 am

Sounds like it is related to Darwin's idea on the correlation of growth.
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Post by alextemplet » Sun Feb 03, 2008 10:40 pm

It is probably an adaptation to walking upright. Don't most apes have longer arms than legs? Perhaps humans had to evolve longer legs to walk upright, and the resulting correspondence of the lenght of arms and legs (or arm span to height, if you prefer) may just be a coincidence once the optimal leg lenght was reached.
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