New research indicates that the dexterity of the thumb, which is characteristic of modern humans, existed as early as about 2 million years ago. Perhaps even some of the earliest members of the genus Homo.
Thumbs, which allowed a firm grip and improved the ability to manipulate objects, gave ancient Homo or a closely related hominid line an evolutionary advantage over contemporaries. Scientists from the University of Tubingen. Eberhard Karl in Germany discovered that the now extinct Australopithecines made and used stone tools, but lacked the human ability to use the thumb, which limited his ability to make tools.
The researchers modeled how the key muscle affects thumb movement in 12 previously found hominid fossils, five 19th century humans, and five chimpanzees. A pair of thumb fossils about 2 million years old from South Africa show agility and strength on par with modern human thumbs.
Scientists disagree over whether the finds in South Africa belong to early Homo or Paranthropus robustus, a dead-end species in hominid evolution. But the dexterity of the thumb of these ancient fossils is comparable to that of representatives of the Homo species, which appeared about 335 thousand years ago. These include Neanderthals from Europe and the Middle East, as well as the South African hominid Homo naledi.
In comparison, Homo or P. robustus possessed thumbs that were more powerful than three australopithecine species several million years old, two of which had previously been assumed to have human-like hands.