Researchers studying the petrified hands of 2-million-year-old hominins concluded that human thumbs at the time had the same range of motion as today. It was the ‘dexterity’ offered in part by the human thumb that enabled us to overcome all other species on earth.
Until now, the ancient origins of the human thumb, and dexterity, have always been dense archaeological mysteries. Through 3D modeling of the muscle movement series in ancient, petrified thumbs, a team of German researchers concluded that it was about 2 million years ago that our early human ancient ancestors developed this key survival tool.
The human thumb: the better to compress with!
The new study was published in the journal Current biology by a team of paleoanthropologists from the University of Tübingen. The researchers digitized ancient hominin fossil thumbs, including those of Homo sapiens (us), in a project riddled with complications.
The biggest problem the research team faced was the fact that fossils do not preserve muscle, and that means we have to rely on the risky approach known as ‘speculation’.
To help them accurately analyze ancient human thumbs, the team of researchers first looked at bone samples from two early-modern humans and four Neanderthal humans, all of whom have lived and died over the past 100,000 years.
Summary of the analytical steps of the study: (A) Model preparation and assumption of power or generational ability of human or chimpanzee (m. Opponens pollicis). (B) Biomechanical efficiency is calculated as the torque generated by m. opponents pollicis at the thumb’s TMC joint. (C) 3D geometric morphometric analysis of proportional bone projection over the metacarpal muscle attachment site. (© 2021 Harvati, Karakostis and Haeufle / Current biology )
An article in Science Power says German scientists analyzed the hands of “the small, cave-dwelling” H. naledi who lived about 250,000 to 300,000 years ago, and also that of a sister species, ‘ Australopithecines. ”
Using 3D technology, the researchers reconstructed the ancient hands and then ‘digitally’ a key muscle known as the ‘ opposens pollicis ”Which is attached to the bottom of the palm and causes the thumb to bend inwards.
The right hand of Australopithecus sediba. (Image by Peter Schmid, thanks to Lee R. Berger and the University of the Witwatersrand. / CC BY-SA 3.0 )
How the human thumb became the powerhouse of evolution
After building their dynamic 3D models from ancient hands, the researchers increasingly applied the model. It was noted that with more applied force ‘better, more precise grips’ were achieved.
According to the authors, it would have ‘helped to hold a needle and thread or swing a hammer’. Finally, the scientists said all the tested members of our generation, Homo, had “basically the same thumb grip strength”, and that it corresponds to the strength measured in the thumbs of modern humans and chimpanzees.
During their experimentation, the team looked at the thumb movements in two hominin samples discovered at the Swartkrans site in South Africa. The authors date from about 2 million years ago and come from an unknown species and say that the Swartkrans fossils are ‘the earliest human thumbs in the fossil record’.
The study notes that compared to these two Swartkrans fossils’ Australopithecines had much weaker thumbs. And although they may be showing instrument-related behavior, according to the authors, they have not yet developed a human level of efficiency.
What this means is that the human thumb as it is today evolved about 2 million years ago in the Homo genus, and that it was the thumb that accelerated the ability of ancient humans to manufacture more intricate stone tools and weapons, which in turn helped us surpass all other homin groups.
This ancient human gives us the “thumbs up” with good reason because the latest study shows that the human thumb is what separates Homo sapiens from the cousins we left behind when we evolved into “uber-human”. ( Zemler / 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, tells CNN that many “assumptions” are made in these types of studies because “muscles are not preserved in the fossil record.” But when she accepted that some speculation was involved in the research, she said the authors of the new article “did an excellent job of dealing with all the complexities in this type of research.” ‘
However, there is another voice that for some other reason needs to insist ‘carefully’ on the conclusions of the new study. Dr Evie Vereecke is an anthropologist and anatomist at the KU Leuven University in Belgium, and although she openly praises the authors’ ‘approach’, she said Science Power the findings should be handled with caution. She said: ‘We [evolutionary scientists] know that ‘agility’ is not just due to one muscle. ”
In other words, agility has an enormous mental component that has not been taken into account in the 3D modeling of the German research team. Therefore, it is not yet known how “competent” people have applied their “super thumbs” in projects that require complicated foresight and the prediction of outcomes.
The full study is available with open access from Elsevier, Current Biology, DOI: https://doi.org/10.1016/j.cub.2020.12.041
Upper print: Researchers used 3D modeling software to reconstruct old hands and then added the critical human thumb muscle to the model. Source: © 2021 Harvati, Karakostis and Haeufle / Current biology
By Ashley Cowie