Researchers studying the petrified hands of 2-million-year-old hominins have concluded that human thumbs back then had the same range of motion as our thumbs do today. It was the “dexterity” afforded in part by the human thumb that enabled us to overpower all other species on Earth.
Until now, the ancient origins of the human thumb, and dexterity, have always been closely locked archaeological mysteries. By 3D modeling the muscle range of motion in ancient, fossilized thumbs, a team of German researchers concluded that it was about 2 million years ago that our early human ancestors first developed this important survival tool.
The human thumb: all the better to squeeze!
The new study was published in the magazine Current Biology by a team of paleoanthropologists from the University of Tübingen. The researchers digitized ancient fossil thumb bones of hominids, including those of homo sapiens (us), in a project full of complications.
The main problem the research team faced was the fact that fossils don’t preserve muscle, and that meant relying on the risky approach known as ‘speculation’.
To help them accurately analyze ancient human thumbs, the team of researchers first looked at hand bone samples from two early modern humans and four Neanderthals who all lived and died over the past 100,000 years.
Summary of the analytical steps of the study: (A) Model preparation and assumption of the ability to generate muscle power in humans or chimpanzees (m. Opponens pollicis). (B) Biomechanical efficiency is calculated as the torque generated by opponents m. Pollicis at the TMC joint of the thumb. (C) 3D geometric morphometric analysis of proportional bone projection over the site of the metacarpal muscle attachment. (© 2021 Harvati, Karakostis and Haeufle / Current Biology )
An article in Science Mag says the German scientists then analyzed the hands of ‘the little cave house’ H. naledi who lived from about 250,000 to 300,000 years ago, “and also those of a sister generation”, Australopithecines. “
Using 3D technology, the researchers reconstructed the old hands and then ‘digitally’ added a key muscle known as the ‘ Opposite thumb It is attached to the base of the palm and allows the thumb to bend 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 power tool of evolution
After building their dynamic 3D models from old hands, the researchers applied more and more force to the model. It was noted that with more applied force, “better, more precise grips” were achieved.
This, according to the authors, would have helped with ‘holding a needle and thread or swinging a hammer’. In conclusion, the scientists said that all members of our lineage tested, Gay, had “essentially the same thumb grip strength,” and that this corresponds to the strength measured in the thumbs of modern humans and chimpanzees.
During their experiments, the team looked at the thumb movements in two humanoid specimens discovered at the Swartkrans site in South Africa. The authors date back to about 2 million years ago, and from an unknown lineage, the authors said these Swartkrans fossils represent “the earliest known hominin thumbs in the fossil record.”
The study notes that compared to these two Swartkrans fossils “ Australopithecines had much weaker thumbs. And while they may have exhibited tool-related behaviors, they had not yet developed human efficiency, the authors say.
What this means is that the human thumb as it is today evolved about 2 million years ago Gay lineage, and that it was the thumb that accelerated the ancient people’s ability to make more complicated stone tools and weapons, which in turn helped us surpass all other human groups.
This ancient human is not giving us the “thumbs up” for nothing, as the latest study shows that the human thumb is the division between Homo sapiens and the cousins we left behind when we evolved into “uber humans”. ( Floors / Adobe Stock)
An excellent research project, but questions remain. . .
Dr. Tracy Kivell, a professor at the University of Kent’s School of Anthropology and Conservation in the UK, told CNN that many “assumptions” are made in such studies because “muscles are not preserved in the fossil record”. But accepting that there was some level of speculation involved in the research, she said the authors of the new paper “have done an excellent job of addressing all the complexities of this type of research.”
There is another voice, however, pushing for “caution” regarding the new study’s conclusions for another reason. Dr. Evie Vereecke is an anthropologist and anatomist at KU Leuven University in Belgium, and while openly praising the authors’ ‘approach’, she said Science Mag the findings should be treated with caution. She said, ‘We [evolutionary scientists] know that agility is not only due to one muscle. ”
In other words, agility has a huge mental component that was not included in the 3D modeling of the German research team. Therefore, it is still unknown how ‘capable’ people applied their ‘super thumbs’ in projects that required complex foresight and predicting results.
The full study is available with open access from Elsevier, Current Biology, DOI: https://doi.org/10.1016/j.cub.2020.12.041
Top image: Researchers used 3D modeling software to reconstruct old hands and then added the crucial human thumb muscle to the model. Source: © 2021 Harvati, Karakostis and Haeufle / Current Biology
By Ashley Cowie