Sunday 19 November 2017

Human hands 'less evolved'

Chimpanzees have grown elongated fingers ideally suited for life in the trees
Chimpanzees have grown elongated fingers ideally suited for life in the trees

Human hands may be less evolved than those of chimpanzees, research suggests.

The strongly held notion that the human hand, with its long opposing thumb, was shaped by intelligent tool-making is misplaced, scientists believe.

Instead it is the chimpanzee whose hands have shown the biggest changes - evolving not to build houses, fly planes or tap computer keyboards, but to hang from branches.

Unlike chimps, but more like gorillas, human hands have long thumbs in relation to their index fingers.

This has been seen as one of the most distinctive traits of humankind and is often cited as one of the chief reasons for our success as a species.

A long opposing thumb makes it easier to pick up and manipulate objects with precision, and has been associated with the invention of stone tools.

But according to the new evidence the basic configuration of the human hand is an ancient one that has changed little over time.

Anatomical analysis shows that thumb-to-finger ratio is much the same in very early humans, people living today, and gorillas, suggesting a link with a dextrous common ancestor.

In contrast chimps belonging to the species family Pan, as well as orangutans, have grown elongated fingers ideally suited for life in the trees.

The scientists led by Dr Sergio Almecija, from Stony Brook University in New York, wrote in the journal Nature Communications: "Humans have only slightly modified finger and thumb lengths since their LCA (last common ancestor) with Pan. This probably occurred with the advent of habitual bipedalism in hominins, and almost certainly preceded regular stone culture."

The researchers measured the hand proportions of humans, living and extinct apes, and the fossil bones of early human ancestors such as Australopithecus.

The findings challenge the idea that a chimp-like hand was the starting point of evolutionary progress towards the modern human hand.

Press Association

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