Feet may be the key to hand evolution

Jan 20, 2010 by Lin Edwards report
foot
Image: Wikimedia Commons.

(PhysOrg.com) -- Scientists in Canada have used a mathematical model to simulate the evolution from an ape-like hand to the modern-day human hand, and discovered that changes in our fingers and hands developed in parallel changes in our toes and feet.

In research reported in the journal , a team of scientists, led by Campbell Rolian from the University of Calgary, took extensive measurements of the feet and hands of chimpanzees (genetically, our closest relatives) and humans to try to find out how the extremities of our chimp-like ancestors might have evolved.

They found there was a definite correlation between measurements of similar areas of the foot and , so for example if the big toe was long, the finger was also long. Dr Rolian speculated the correlation between toes and fingers may be because they share a similar genetic “blueprint”, so minor changes to the blueprint would affect both hands and feet.

Once they had the anatomical measurements, the team used the data to create a of the evolution of the hands and feet from those of our chimp-like ancestors to humans. The model simulated the evolutionary pressures and changed the shape of the feet or hands in small increments to see what effects the changes would have. They discovered that changes made to the feet also caused corresponding changes to the hands, particularly in the relative lengths of fingers and toes, and Dr Rolian said these changes may have allowed the hands of early hominins, including , the dexterity required to use stone tools.

The scientists say the capacity to walk upright on two feet is linked intrinsically to the emergence of the use of stone tools. Dr Rolian said the findings go “back to Darwin’s The Descent of Man,” since Darwin was one of the first scientists to consider there might be a link between walking upright and using . But Darwin’s idea was that bipedalism evolved first, and this freed the hands, which could then be used for purposes other than locomotion, while Rolian’s work suggests they evolved together.

Professor Robin Crompton at Liverpool University in the UK, said the feet and hands of chimpanzees may not necessarily be good models for those of human ancestors, and suggested the extremities of lowland gorillas may be more “interesting” in this respect. He also said the shape and biomechanics of hands and were more complex than simple anatomical measurements might suggest.

Professor Crompton is head of the university’s Primate Evolution and Morphology Research Group. His research has found that orang-utans, which are tree dwellers, are more like modern humans in bipedal walking than the , and his work suggests bipedalism may even have arisen as early as 24 million years ago.

Explore further: Evolution of marine crocodilians constrained by ocean temperatures

More information: THE CO-EVOLUTION OF HUMAN HANDS AND FEET, Evolution, DOI:10.1111/j.1558-5646.2009.00944.x

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User comments : 3

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Phelankell
1 / 5 (3) Jan 20, 2010
Considering our tree dwelling past I'd think that hands were evolved first and feet followed.
Parsec
5 / 5 (2) Jan 20, 2010
Given the intense societal and cultural significance of the fingers, I find it more likely that the hand is in fact one of natures do overs. All of those primates that had to stop to give pursuers the middle toe were selected out of the gene pool, and mother natures only real alternative was to evolve a middle finger capable of the same advanced descriptive power.
jonnyboy
not rated yet Jan 20, 2010
I am not sure how relevant this is considering that most researchers now believe that we evolved from a common ancestor
Benier_Duster
Jan 21, 2010
This comment has been removed by a moderator.