A new study has challenged the old belief that the human hand is more evolved than that of primates like the chimpanzee. According to its findings, our hands are more primitive than we would have thought while those of chimps have undergone more changes (and are thus more evolved) throughout time. The paper has been published in Nature Communications.
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A team of researchers studied the hands of modern primates and the remains of early ones. They analysed the thumb to finger length, a proportion which differs from humans to chimps. While humans have a relatively longer thumb as opposed to the other fingers thus resulting in opposable thumbs, chimps have longer and narrower hands and their thumbs are not opposable. It might make more sense that this difference is accounted by evolution to allow humans to adapt to their environment – to hold tools, for instance – and that those of chimps are more primitive. However, the results from the study of the two types of hands hint at the opposite.
“Human hands have not changed much,” said one of the authors, Sergio Almécija from Stony Brook University in New York, in a statement to IFLScience. “Hands were already like ours today in prehistoric times.”
The older primates studied were the Ardipithecus ramidus (5.6 million years ago) and the Australopithecus sediba (2 million years ago). The huge age gap did not lead to different types of hands in terms of thumb and finger size though. However, chimps grew longer hands in that time, allegedly to be able to hang onto branches better.
“Our hypothesis is that the hand proportions that facilitate a refined human-like ‘pad-to-pad’ precision grasping are one of the earliest adaptations in hominins,” said Almécija.
Hominin hands seem to have been modified to a very small extent, and thus according to Almécija, the hand proportions of A. ramidus most probably resemble the last common ancestor of humans and chimps which would have been alive around 13 million years ago. As such, human hands might date further back.
Thus, according to the research, the hands of the ancestors of humans were similar to ours today. They believe this holds true even if the use of tools only began 3.3 million years ago. They explain this apparent discrepancy by suggesting that the adaptations of humans to the use of tools were of a neurological nature, and not of a physical one.
Almécija further delved into possible explanations, saying that their results would imply that the common ancestor of humans and chimps was more likely human-like than chimp-like.
“The results of our study show that the hand proportions of living apes are not as similar as previously assumed. In fact, gorillas and chimpanzees are more different from each other than chimpanzees from orangutans, or those from gibbons.”
He also mentioned the possibility of other anatomical human parts being more primitive.