The human hand, a marvel of evolution that allows our species to use tools with unique dexterity, may owe its origin to changes in a critical genetic switch.

Research has identified passages of DNA that appear to be involved in forming the human thumb and big toe, which are important to the deft grip and upright posture that are among the defining features of Homo sapiens. These areas of the genome have altered markedly since the human family tree branched out from that of chimpanzees about 6 million years ago, and may be among the evolved genetic changes that formed our species.

They may well have played a part in the development of opposable thumbs and larger big toes, two characteristics that set humans apart from chimps.

“Our study identifies a potential genetic contributor to fundamental morphological differences between humans and apes,” said James Noonan, of Yale University School of Medicine. He led the research, which also involved scientists at the MRC Human Genetics Unit at Western General Hospital in Edinburgh.

The findings, published in the journal Science, offer tantalising evidence of a genetic switch that is pivotal to the formation of these important human digits.

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