Research press release


Nature Communications

Evolution: Human hands may be more primitive than chimp's



今回、Sergio Almecijaたちは、ヒト、生きている類人猿、類人猿の化石、ヒトの祖先種(Ardipithecus ramidus、Australopithecus sedibaなど)の化石について、手のプロポーションを測定して、手の段階的進化について解明を進めた。今回の研究では、チンパンジーとオランウータンにおいて指の伸長の収斂進化が最近になって起こり、ヒトとヒトの祖先種、ゴリラの場合には比較的わずかな変化しか生じなかったことが明らかになった。


Human hand proportions have changed little from those of the last common ancestor of chimpanzees and humans suggests a study in Nature Communications. These findings indicate that the structure of the modern human hand is largely primitive in nature, rather than the result of selective pressures in the context of stone tool-making.

Human hands exhibit a long thumb-to-fingers ratio, which refers to the length of the thumb in relation to the index fingers. It is one of the most distinctive traits of humankind compared to apes and is often cited as one of the reasons for the success of the species. However, there are competing theories on how the human hand evolved over time.

Sergio Almecija and colleagues measure the hand proportions of humans, living and fossil apes, as well as fossils of human ancestors including Ardipithecus ramidus and Australopithecus sediba, to understand the stepwise evolution of the hand. Their results show the more recent, convergent evolution of finger elongation in chimpanzees and orangutans and comparatively little change between humans, human ancestors and gorillas.

These results support the hypothesis that the long thumb-to-fingers ratio of the human hand was acquired convergently with other highly dexterous anthropoids. The findings of the study also challenge the assumption that a chimp-like hand was the starting point of the chimpanzee-human last common ancestor.

doi: 10.1038/ncomms8717

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