By opening the way for hands to evolve

Jan 18, 2010 11:58 GMT  ·  By
The human hand may have evolved to fulfill its current functions because our feet grew as well
   The human hand may have evolved to fulfill its current functions because our feet grew as well

Undoubtedly, the most important stage in our evolution took place when we learned to use our hands to create tools. These innovations would go on to become the hallmark of our species, as most of the things we do, or are capable of, today are in some way or another connected to tools. But a team of anthropologists argues that our ability to craft tools was only made possible when changes in our feet occurred. Walking upright was the main element that eventually allowed our hands to be free of the burden of carrying us around. It was then that they became small and sensitive enough to allow for the manipulation of small objects, the BBC News reports.

“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,” the leader of the new study, Campbell Rolian, explained. He is a scientist at the University of Calgary in Canada, and also the main investigator of the team that used a mathematical model to come to this conclusion. Other groups disagree with the findings.

Rolian and his team founded their model on extensive measurements of human and chimpanzee hands and feet. They reveal that the two body parts are intimately correlated in terms of size. For example, the expert said, a long toe on a foot was very likely to correspond to a large thumb, on the hand of the same individual. “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,” Rolian added. All of these anatomical data were then put together in the mathematical model, which was designed specifically to simulate the pressure evolutionary change placed on hands and feet.

Across both species, the model evidenced the fact that the relative proportions of the fingers and toes remained the same. In other words, changes in the size of the toes were also reflected in the size of the thumbs. Some of the early hominins, such as the Neanderthals, might have gained their ability to use stone tools because their feet needed to grow to support their bipedal walking style. There are some researchers, however, who believe that the new investigation raises some interesting questions as well.

“I am not personally convinced that the foot and hand of chimpanzees are a good model [of human ancestors' hands and feet] – the foot of the lowland gorilla may be more interesting in this respect,” Liverpool University Professor of Biology Robin Crompton said of the work. The biomechanics, shape and functions associated with the lowland gorilla foot makes it an ideal candidate for human comparison, the scientist shared.