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Researchers studying the fossilized hands of hominids from 2 million years ago concluded that human thumbs back then had the same ranges of motion as our thumbs today. It is the “dexterity” offered in part by the human thumb that has enabled us to master all other species on Earth.
Until now, the ancient origins of the human thumb and dexterity have always been closely related archaeological mysteries. By 3D modeling the range of muscle motion in ancient fossilized thumbs, a team of German researchers concluded that around 2 million years ago our first human ancestors developed this key survival tool.
The human thumb: so much the better for squeezing!
New study was published in the newspaper Current biology by a team of paleoanthropologists from the University of Tübingen. Researchers scanned ancient fossil thumb bones of hominids, including those from homo sapiens (us), in a project strewn with pitfalls.
The main problem the research team faced was the fact that the fossils did not preserve muscle and this involved relying on a risky approach known as “speculation.”
To help them accurately analyze ancient human thumbs, the team of researchers first examined hand bone samples from two early modern humans and four Neanderthals who had all lived and died within 100,000. last years.
Summary of the analytical steps of the study: (A) Preparation of the model and hypothesis of the capacity of generation of human or chimpanzee muscle force (m. Opposens pollicis). (B) Biomechanical efficiency is calculated as the torque generated by m. adversens pollicis at the TMC thumb joint. (C) 3D geometric morphometric analysis of the proportional bone projection through the attachment site of the metacarpal muscle. (© 2021 Harvati, Karakostis and Haeufle / Current biology )
An article in Science Mag said that the German scientists then analyzed the hands of “the tiny cave dwelling H. naledi who lived about 250,000 to 300,000 years ago, “and also those of a brother kind”, Australopithecus. “
Using 3D technology, the researchers reconstructed the old hands, then “digitally” added a key muscle known as “ Opposite thumb Which is attached to the base of the palm and allows the thumb to flex inward.
The right hand of Australopithecus sediba. (Image by Peter Schmid, courtesy Lee R. Berger and the University of the Witwatersrand./ CC BY-SA 3.0 )
How the human thumb became the powerful tool of evolution
After building their dynamic 3D models of ancient hands, the researchers applied increasing force to the model. It has been observed that with more force applied, “better, more precise grips” were obtained.
This, according to the authors, would have helped “to hold a needle and thread firmly or to swing a hammer”. In conclusion, scientists said that all tested members of our genus, Homo, had “basically the same thumb grip strength,” and that this matches the force measured in the thumbs of modern humans and chimpanzees.
During their experiment, the team examined the thumb movements of two hominid specimens found at the Swartkrans site in South Africa. Dating from around 2 million years ago and of an unknown genre, the authors said these Swartkrans fossils represent “the earliest known human inches in the fossil record.”
The study notes that in comparison with these two fossils from Swartkrans ” Australopithecus had much smaller thumbs. And while they may have exhibited tool-related behaviors, they had yet to develop a level of human efficiency, according to the authors.
This means that the human thumb as it is today evolved around 2 million years ago in the Homo genre, and that it was the thumb that accelerated the ability of ancient humans to craft more complicated stone tools and weapons, which helped us outperform all other hominid groups.
This ancient human gives us a “thumbs up” for good reason because the latest study shows that the human thumb is what separates Homo sapiens from the cousins we left behind as we progressed to “uber-humans”. ( Floors / Adobe Stock)
An excellent research project but questions remain. . .
Dr Tracy Kivell, professor at the School of Anthropology and Conservation at the University of Kent in the UK, said CNN that many “assumptions” are made in these types of studies because “muscles are not preserved in the fossil record”. But accepting that a certain degree of speculation was involved in the research, she said the authors of the new article “did a great job of dealing with all of the complexities involved in this type of research.
https://www.youtube.com/watch?v=RUL8hKDdY84
However, there is another voice that urges “caution” about the new study’s findings for another reason. Dr Evie Vereecke is an anthropologist and anatomist at the Belgian University of KU Leuven, and while openly praising the authors’ “approach”, she said Science Mag results should be treated with caution. She said: “We [evolutionary scientists] know that “dexterity” is not just due to a muscle. ”
In other words, dexterity has a massive mental component that was not taken into account in the 3D modeling of the German research team. As a result, it is still unclear how “capable” humans applied their “super-thumbs” in projects that required complex forecasting and prediction of outcomes.
The full study is available in open access from 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, then added the critical human thumb muscle to the model. Source: © 2021 Harvati, Karakostis and Haeufle / Current biology
By Ashley Cowie
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