How human hands evolved to make and manipulate stone tools

January 19th, 2010 - 2:30 pm ICT by ANI  

London, January 19 (ANI): A mathematical model may have solved the mystery of how human hands became nimble enough to make and manipulate stone tools.

According to a report by BBC News, the team of scientists that developed the model said that changes in our hands and fingers were a side-effect of changes in the shape of our feet.

This shows that the capacity to stand and walk on two feet is intrinsically linked to the emergence of stone tool technology.

The scientists used a mathematical model to simulate the changes.

“This goes back to Darwin’s The Descent of Man,” said Campbell Rolian, a scientist from the University of Calgary in Canada who led the study.

“Charles Darwin was among the first to consider the relationship between stone tool technology and bipedalism,” he said.

“His idea was that they were separate events and they happened sequentially - that bipedalism freed the hand to evolve for other purposes,” he added.

“What we showed was that the changes in the hand and foot are similar developments and changes in one would have side-effects manifesting in the other,” he explained.

To study this, Dr Rolian and his colleagues took measurements from the hands and feet of humans and of chimpanzees.

Their aim was to find out how the hands and feet of our more chimp-like ancestors would have evolved.

The researchers’ measurements showed a strong correlation between similar parts of the hand and foot.

“So, if you have a long big toe, you tend have a long thumb,” Dr Rolian explained.

“One reason fingers and toes may be so strongly correlated is that they share a similar genetic and developmental ‘blueprint’, and small changes to this blueprint can affect the hand and foot in parallel,” he said.

With this anatomical data, the researchers were able to create their mathematical simulation of evolutionary change.

“We used the mathematical model to simulate the evolutionary pressures on the hands and feet,” Dr Rolian explained.

This model essentially adjusted the shape of the hands or the feet, recreating single, small evolutionary changes to see what effect they had.

By simulating this evolutionary shape-shifting, the team found that changes in the feet caused parallel changes in the hands, especially in the relative proportions of the fingers and toes.

According to Dr Rolian, these parallel changes may have been an important evolutionary stem that allowed human ancestors, including Neanderthals, to develop the dexterity for stone tool technology. (ANI)

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