Researchers studying the fossilized hands of 2-million-year-old hominins have concluded that human thumbs back then had the same ranges of motion as our current thumbs. It was the “dexterity” offered in part by the human thumb that allowed us to surpass all other species on Earth.
Until now, the ancient origins of the human thumb and dexterity have always been well-closed archaeological mysteries. Using 3D modeling of the range of motion of muscle in ancient fossilized thumbs, a team of German researchers has concluded that it was approximately 2 million years ago that our ancient human ancestors first developed this key survival tool. .
The human thumb: better to squeeze!
The new to study was published in the journal Current biology by a team of paleoanthropologists from the University of Tübingen. Researchers digitized ancient fossil thumb bones of hominins, including those of homo sapiens (us), in a project full of complications.
The main problem the research team faced was the fact that fossils do not preserve muscles and this meant relying on the risk approach known as “speculation”.
To help them accurately analyze ancient human thumbs, the team of researchers first examined bone samples from two early modern humans and four Neanderthals that had lived and died for the past 100,000 years.
Summary of the analytical steps of the study: (A) Model preparation and assumption of the ability to generate human or chimpanzee muscle strength (m. Opponens pollicis). (B) Biomechanical efficiency is calculated as the torque generated by m. opposens thumbs to TMC joint of thumb. (C) 3D geometric morphometric analysis of the proportional projection of bones through the junction site of the metacarpal muscle. (© 2021 Harvati, Karakostis and Haeufle / Current biology )
An article a Science Mag says German scientists analyzed the hands of “the tiny rock dwelling H. naledi who lived about 250,000 to 300,000 years ago, “and also those of a sister genus” Australopithecus“.
Using 3D technology, the researchers rebuilt the old hands and then “digitally” added a key muscle known as ” Opposite thumb ”It attaches to the base of the palm and allows the thumb to flex inward.
The right hand of Australopithecus sediba. (Image by Peter Schmid, courtesy of Lee R. Berger and the University of the Witwatersrand./ CC BY-SA 3.0 )
How the human thumb became the powerful tool of evolution
Having built their dynamic 3D models from ancient hands, researchers applied increasing force to the model. It was observed that with a more applied force “better and more precise grips” were achieved.
This, according to the authors, would have helped “hold a needle and thread firm or turn a hammer.” In conclusion, scientists said that all proven members of our genus, Homo, it had “basically the same thumb holding force,” and this coincides with the force measured on the thumbs of modern humans and chimpanzees.
During their experimentation, the team examined the movements of the thumb in two specimens of hominins discovered at the Swartkrans site in South Africa. The authors, who date from about two million years ago and come from an unknown genus, said that these Swartkrans fossils represent “the first known human thumbs in the fossil record.”
The study notes that compared to these two fossils of Swartkrans ” Australopithecus he had much weaker thumbs. ”And while they may have exhibited tool-related behaviors, they had not yet developed a level of efficiency similar to humans, according to the authors.
This means that the human thumb as it is today evolved about 2 million years ago in the Man gender, and it was the thumb that accelerated the ability of ancient humans to make more complicated stone tools and weapons, which in turn helped us surpass all other groups of hominins.
This ancient human gives us the “thumbs up” for a good reason because the latest study shows that the human thumb is what separates Homo sapiens from the cousins we left as we evolved into “humans”. ( Soil / Adobe Stock)
An excellent research project, but questions remain. . .
Dr Tracy Kivell, a lecturer in the Faculty of Anthropology and Conservation at the University of Kent in the UK, said CNN that many “assumptions” are made in this type of study because “muscles are not preserved in the fossil record”. But accepting that there was some degree of speculation in the research, he said the authors of the new article “did an excellent job dealing with all the complexities involved in this type of research.”
However, there is another voice urging “caution” towards the conclusions of the new study for another reason. Dr. Evie Vereecke is an anthropologist and anatomist at the Belgian university KU Leuven, and while she openly praises the authors’ “approach,” she said. Science Mag conclusions should be handled with caution. She said, “We [evolutionary scientists] know that “dexterity” is not just due to a muscle. ”
In other words, dexterity has a huge mental component that was not taken into account in the 3D modeling of the German research team. Therefore, it is not yet known to what extent “capable” humans were applying their “superpoles” in projects that require complex prediction and prediction of results.
The full study is available with open access to Elsevier, Current Biology, DOI: https://doi.org/10.1016/j.cub.2020.12.041
Top image: The researchers used 3D modeling software to reconstruct old hands and then added the critical human thumb to the muscle. Source: © 2021 Harvati, Karakostis and Haeufle / Current biology
By Ashley Cowie