Stone tools shaped human hands

A new fossil belonging to the oldest known anatomically modern hand suggests the strength and dexterity needed to make and use the latter tools quickly shaped our hands into what they are today,’New Scientist’ reported.

A team led by Fredrick Kyalo Manthi of the National Museums of Kenya had discovered an intriguing bone in 2010. Carol Ward of the University of Missouri and colleagues identified it as a third metacarpal,the long bone in the palm between the middle finger and the wrist.

Like modern human metacarpals,it has a small lump at its base – the styloid. This projection helps stabilise the wrist when the hand is gripping small objects between the thumb and fingers.

Isotope dating revealed the bone to be about 1.4 million years old. It is likely to have belonged to Homo erectus. Hand bones of early Homo erectus are almost unknown,said Richard Potts of the Smithsonian Institution in Washington DC.

“Having such a well-preserved specimen begins to answer questions about hand evolution,” he said. According to Mary Marzke of Arizona State University,it

shows that our ancestors’ hands were already evolving into their modern form 1.4 million years ago.

The forceful,repetitive and sustained processes of tool use,such as digging with rocks,would have made stronger hands desirable,said Marzke.

Researchers said this would have been particularly useful for knocking off flakes to form and sharpen hand axes. Once the important wrist features were in place,it became easier for later hominids to make smaller,finer tools.

Ward’s team believes it is the first evidence of anatomy evolving to suit a new technology. As stone tools became more widespread,those who had the wrist structure to use them would have had an evolutionary advantage. “The way we look today has been shaped by our behaviour over millions of years,” said Ward.