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# Nine People in Ten Are Right-Handed
- URL: https://theparnassian.com/en/deviat-iz-desiati-liudei-pravshi/
- Published: 2026-05-19T12:42:23.000Z
- Updated: 2026-10-01T05:26:05.000Z
- Author: Alexandr Radayev
- Tags: Archaeology, Science, Nature

Nine people in ten are right-handed. Other primates show no such picture: chimpanzees and gorillas may also prefer one hand, but far less often and far less markedly. Scientists have long been trying to work out why humans, specifically, have gone so far. There is no shortage of hypotheses: tools, diet, body size, social structure, the development of the brain, the transition to walking upright. But none of them, taken alone, explained the skew.

A team led by Thomas Püschel of Oxford tested all the hypotheses at once. The authors gathered data on 2,025 individuals of 41 species of monkeys and apes and ran them through a statistical model that takes account of kinship between species. Without such a correction the results are usually distorted. If two species resemble each other, the likeness may come from a common ancestor rather than a common cause. The model helps to tell genuine connections from false coincidences.

Taken separately, no single trait worked, and humans remained an exception all the same. The explanation was supplied by a combination of two traits: the size of the brain and the ratio of arm length to leg length, by which upright walking is judged. When these two factors were accounted for simultaneously, humans ceased to be an exception and slotted into the general primate series. It turns out that the matter lies neither in a large brain nor in upright walking in themselves, but precisely in their combination.

The model was then applied to fossil ancestors. From skulls and bones, scientists know both the size of their brains and their bodily proportions. The result was a consistent curve. Ardipithecines and australopithecines preferred the right hand only weakly, roughly like today's chimpanzees. With the appearance of the genus Homo the skew grows. Modern humans stand at the far end of this curve.

If the explanation is correct, it ought to work in reverse as well. In a species with a small brain and incomplete upright walking, right-handedness should be weak. Evolution offers just such a case in the Flores "hobbit", Homo floresiensis. This is a late species of the genus Homo, yet its brain was small, and the structure of its body was still suited to climbing trees. The model predicts that right-handers occurred among them with roughly the same frequency as among australopithecines three million years ago. That is, there was no mass skew to the right.

A different question remains open: why, under such strong selection, did evolution nevertheless preserve left-handers?

![](https://theparnassian.com/content/images/2026/09/photo_20594@19-05-2026_15-42-23.jpg)