New discoveries by the scientists may have solved the mystery of how human hands became nimble enough to make and manipulate stone tools. The team reports in the journal Evolution, through BBC News that changes in our hands and fingers were a side-effect of changes in the shape of our feet. This, they say, 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. Other researchers, though, have questioned this approach.
According to Campbell Rolian, a scientist from the University of Calgary in Canada who led the study, said: “This goes back to Darwin’s The Descent of Man. “[Charles Darwin] was among the first to consider the relationship between stone tool technology and bipedalism.”His idea was that they were separate events and they happened sequentially – that bipedalism freed the hand to evolve for other purposes. “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.”
To study this, Dr Rolian and his colleagues took measurements from the hands and feet of humans and of chimpanzees. The 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.
With this anatomical data, the researchers were able to create their mathematical simulation of evolutionary change. This model 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.
These parallel changes or side-effects, said Dr Rolian, may have been an important evolutionary stem that allowed human ancestors, including Neanderthals, to develop the dexterity for stone tool technology.
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