The discovery of an ancient, hominid hand bone, a third metacarpal with styloid process, has sent a flurry of excitement through the paleoanthropological world, and could answer some important questions about the development of tool-making. Carol Ward, of the University of Missouri, published the find online in the Proceedings of the National Academy of Sciences on December 16. It’s very rare to find fossil hand or foot bones, as bodily extremities tend to get lost at the time of death, through the attentions of scavengers, or through geological activity in the succeeding eons. This find near Lake Turkana in Kenya, dated at 1.42 million years old, precedes any similar artefact by 500,000 years, and is very significant in the efforts to understand the evolution of hominid lineage.
The third metacarpal is located down the centre of the hand and attaches to the wrist. What is particularly interesting about this example, apart from its age, is its styloid process, a small piece of bone that locks the third metacarpal into the wrist. This allows the thumb and fingers to exert increased pressure on the wrist and palm, giving much more control when making and using tools. Up to now the only hominid species found with this adaptation were Homo sapiens and their close cousins, the Neanderthals. This find pushes the estimated date of the evolution of the styloid process back to early Homo erectus, the undisputed predecessor of both species.
Whilst other primates have been observed to use, and sometimes make, simple tools, hominids exceeded them at least 2.5 million years ago with their crude and clunky flint hand axes, a technology called “Oldawan”. The hominids of that time probably also used the flakes left over from the axe fashioning process, for cutting flesh and plants. Oldawan technology continued to be used until 1.2 million years ago, but was eventually superseded by Acheulean technology, which first appeared about 1.6 million years ago. Acheulean tools are more sophisticated, more varied, and have much longer cutting edges. As anyone attempting to make such a tool knows, they require a great deal of dexterity and skill to produce. It seems likely that the adaptation of the third metacarpal bone with a styloid process, together with the increased cognitive abilities of Home erectus, made possible the revolution from Oldawan to Acheulean technology.
Fired with the enthusiasm for this find, Carol Ward and her colleagues hope to find even earlier examples of this third metacarpal adaptation but, given the rarity of any kind of hand bone discovery, this may be optimistic. What they have already found, however, ranks among the most important paleontological discoveries of the decade. It removes yet another “missing link”, connecting us to our evolutionary forebears.
Mark A Jordan graduated in Philosophy from the University of Leicester in 1982. He has worked variously as a political activist on the left, freelance journalist, creative writer, market researcher, supported housing manager and music promoter. He is currently researching the philosophy and history of science. You can reach Mark at firstname.lastname@example.org
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