science

The study found that human thumb got a major upgrade two million years ago, leading to a cultural revolution

The study found that human thumb got a major upgrade two million years ago, leading to a cultural revolution

Image showing the muscle model used to calculate the biomechanical efficiency of the thumb.

Image showing the muscle model used to calculate the biomechanical efficiency of the thumb.
picture: Katrina Harvati, Alexandros Caracostis, Daniel Heifel

The human thumb is an evolution marvel, allowing our ancestors to forge stone tools and radically expand their food options. New research suggests that our graceful and graceful thumbs appeared two million years ago, in an evolution that irreversibly changed the course of human history.

Many primates have opposing thumbs, but no one is quite like ours. The human thumb, which contrasts with other fingers, allows precise grasping, which anthropologists consider an essential physical feature of drafting tools.

Scientists are naturally interested to know when this added prowess developed And whether it coincided with the emergence of stone tool production and other cultural innovations.

Most of the studies looking at the history of hominin ingenuity are based on direct comparison between the modern human hand and the hands of early hominins, says Katrina Harvati, lead author of the new study and an ancient anthropologist at the University of Tübingen. New research challenges this methodological approach Instead, it evaluates each organization on its own merits. It is possible, in theory, that an earlier version of the hominin hand was better for thumb dexterity.

As a reminder, our human race, Homo sapiens, Which appeared about 300,000 years ago, which means we are late in the human presentation. Other humans (now extinct), such as to turn downAnd the Standing manAnd the Nalidi manAnd and Neanderthalensis (Also known as Neanderthals) existed much earlier, with the first humans appearing about 2.8 million years ago And maybe even before that.

Key to the new studyAnd the Published today in Current Biology, it is an anatomical concept known as “thumb opposition.” Harvati explained in an email that this is a “thumb-to-finger contact”. She said this efficiency “improves dramatically in humans” compared to other primates such as Chimpanzee (who also has a contralateral thumb) is an “essential component of human-like manual dexterity”.

Going to the new study, Harvati and her colleagues wanted to see if the enhanced thumb-opposition efficiency in early hominin fossils could be discovered, and if so, what were those fossils. Given that some of the oldest stone tools in the archaeological record date back more than 3 million years ago, it seemed possible that another race of hominins could exist, namely: Ostropithecus, And it was too The versatility of the human thumb. The appearance of a somewhat rough thumb, tied to the timeline of the cultural development of humanity, was another line of investigation the team pursued.

For the researchers’ analysis He studied the hand fossils of modern humans, chimpanzees, and a large number of hominins of the Pleistocene, including NeanderthalensisAnd the Nalidi man, Three types of Australopithecus, And two specimens found at the Swartkrans site in South Africa, presumably from an early But it is not known to turn down Species or Paranthropus robustus (Which you might already be a member of Australopithecus). The researchers took two factors into account for the analysis: Inferred anatomy of bone and soft tissue.

“Since the muscles themselves are not conserved in fossils, we infer their presence and location in the skeleton of the hand based on their distinct attachment regions on the surface of the bones,” Harvati writes. It is noteworthy that our study focused on the muscle, the opponent pollicis, whose overall position, function, and muscle attachment sites are equivalent among great apes, providing a suitable comparative basis for our sample.

Image showing the difference between the human and chimpanzee thumb muscles.

Image showing the difference between the human and chimpanzee thumb muscles.
picture: Katrina Harvati, Alexandros Caracostis, Daniel Heifel

Taken together, this allowed scientists to create virtual models of hominin hands and calculate the manual dexterity available to each species.

“Our methodology combines the virtual modeling of evolved muscles with the 3D analysis of bone shape and size,” said Alexandros Caracostis, an ancient anthropologist at the University of Tübingen and first author of the study, in the Cell Press. statement.

The results showed that all humans from the Pleistocene epoch who were evaluated in the study demonstrated Increasing the efficiency of the opposition of the thumb, highlighting “the significance of this functional feature in the biocultural development of our species,” the team wrote in their paper.

This ingenuity was seen in Nalidi man, A small-brained human not associated with stone tools, and in 2-Million-year-old bones were found at the Swartkrans Cave site in South Africa, setting a time frame for the emergence of this morphological feature. Indeed, as the authors emphasize, this time period coincides with increasing levels of tool use in Africa and the emergence of cultural complexity.

Our study indicates that this human ability, or increased thumb opposition efficiency, or thumb dexterity, was indeed evolved at the dawn of to turn down Proportions It was perhaps a crucial foundational building block for the very important biocultural developments that took place two million years later, ”Harvati explained. “This includes the regular use of stone tools, the development of more complex stone tool industries, the gradually increasing exploitation of animal resources, and of course the emergence of Standing man, Of the hominins with large brains and with a larger body, whose geographical scope included both Africa and Eurasia.

At the same time, however, the dexterity of the thumb Australopithecus It has been found to be similar to a live chimpanzee. This is somewhat surprising, but members of this genus are He would still have been able to use tools, as he is today with chimpanzeesAccording to Harvati. Moreover, they may have produced the oldest stone tools, namely The oldest They are found in Kenya and date back nearly 3.3 million years. in spite of that, Australopithecus “He has not yet developed the increased ingenuity that has been observed in humans,” Harvati said. Australopithecus Sidiba, “Whose hand, especially the thumb, has been described as particularly human-like, which leads to suggestions that it is related to device-related behaviors.”

Irene Marie Williams Hatalla, associate professor of biology at Chatham University was not Participate in the new research, have some problems with Paper, citing the focus on a single muscle-attachment site, known as anchorage, as a major limitation.

In an email, the authors use “aspects of the shape and size of the muscle attachment complex to approximate the shape and functional capabilities of the small muscle attached to the hand.” This particular muscle is very important for moving the thumb, but “the idea that muscle morphology – and thus muscle function and organism – can be deduced from the attachment site associated with it is an ancient and very tempting idea that is still the subject of much debate,” said Williams Hatalla.

Basically, “We simply do not understand the relationship between the morphology of the attachment sites and the morphology, and certainly not the functional ability of the attached muscle, to say with confidence anything about the latter based on the former,” she said.

Harvati admitted that an important limitation of her team’s study was that they were only able to focus on one “albeit critical” muscle of the thumb. She said this was “necessary because of the fragmented nature of the fossil record” and because her team “wanted to include as many samples as possible from the largest possible number of hominin species”.

Looking to the future, Harvati would like to investigate other important fingers and muscles used in human-like tools And the Study the remains of early hominins, incl AustralopithecusTo learn more about their behaviors and use possible tools. It also plans to study the hands of Neanderthals, who were so slightly different from U.S.

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