Human thumbs are two million years old, according to reports in Science (AAAS) News and SciTech Daily 28 January and Current Biology 28 January 2021 doi: 10.1016/j.cub.2020.12.041.
Scientists at the University of Tübingen made computer models of thumb bones from “a variety of ancient hominins” along with those of modern humans and chimpanzees, and used these to study the attachment site of a muscle named opponens pollicis. This muscle attaches to the bone that underlies the base of the thumb, and lifts the thumb away from the palm of the hand and pulls it to face the fingers, thus facilitating the ability to grasp and manipulate objects.
From their examination of the attachment sites they worked out how much strength the muscle could exert when grasping objects. They found all the thumbs classified as Homo, i.e. “early modern humans”, Neanderthals and Homo naledi had the same grip strength as modern humans, while the bones identified as Australopithecus had a lesser grip strength, similar to chimpanzees.
They also found that fossils from a site in Swartkrans in South Africa would have had human-like grip strength. The Swartkrans fossils are very incomplete and have yet to be classified, but because they have been dated as two million years old the research team concluded “a fundamental aspect of efficient thumb opposition appeared approximately 2 million years ago, possibly associated with our own genus Homo, and did not characterize Australopithecus, the earliest proposed stone tool maker.”
Editorial Comment: In spite of the popular belief that Australopithecines are human ancestors, they are really a group of extinct apes, so it is no surprise they would have thumbs like chimpanzees. Neanderthals and “early modern humans” are all just humans so it is no surprise they have thumbs like living humans.
As the reports above indicated, the Swartkrans fossils are a collection of bone fragments and teeth, some of which look like human bones and teeth. Therefore, it is likely the thumb bone used in this study is human. The only reason they would not be considered human is the old date assigned to the site.
Homo naledi is also a collection of individual bones and bone fragments found in a cave. It is quite likely there are human bones among them. For more details on these bones see the question: Is the discovery of Homo naledi in South Africa evidence for apes evolving into humans? Answer here.
We would ask the research team how they think human-like thumbs “appeared” two million years ago. What happened to ape hands to change them to human hands. In fact, there are many large differences between human and ape hands that involve more than just one muscle. Ape hands are designed for strength and support, with a short thumb, a long palm region and short curved robust fingers that support the body whilst climbing around tree branches or when knuckle walking on the ground. With this hand structure their thumbs are only partially opposable, but enough for them to pick fruit and other objects and use some simple tools like rocks and sticks. But not enough to paint like Rembrandt or selectively poke like Next Gen man on an iPhone.
For more on ape and human differences see the question: Man, apes and monkeys: what are the differences? Answer here.
Creation Research News 10 February 2021
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