70% of wild gorillas in Japan-led study found to be right-handed

KYOTO -- A team led by a Kyoto University researcher observing a group of western lowland gorillas in the wild found that about 70% of the mammals were right-handed.

The findings were published on Jan. 11 in the online edition of the American Journal of Physical Anthropology.

Although there have been numerous reports on the dominant hand of tamed primates in zoos and other places on an individual basis, there have been few instances where analysis was conducted on a whole group living in the wild. According to the research team, the recent findings were the result of observing a specific group, and thereby cannot be used to conclude that gorillas are right-handed in general. However, the discovery could contribute to existing theories on the human acquisition of a dominant hand.

The research was conducted over a total of 331 days between August 2017 and December 2019. The team observed 21 western lowland gorillas inhabiting a national park in Gabon in central Africa, and recorded 4,293 instances of the apes feeding on African ginger. There was no significant difference in which hand the gorillas used when they pulled out ginger from the ground with one hand. Meanwhile, for the detailed work of taking out the pith at the center of ginger stems with one hand while holding the stem with the other, 15 gorillas, or around 70%, extracted the pith with their right hand -- markedly greater in number than the six apes that used their left.

The use of language was previously thought to be a factor in people acquiring a dominant hand. However, more cases have been reported where primates other than humans use a certain hand frequently as if it were their dominant hand. This has given rise to the hypothesis that the dominant hand may be attained before language.

The research team will continue investigations into the mechanism of the gorillas' dominant hand, while also comparing the data to that of humans.

Masaya Tamura, a doctoral student studying primatology at Kyoto University's Graduate School of Science, commented, "There is a lot that is unknown about the dominant hand. I hope that this will contribute to understanding and research of the evolution of the dominant hand."

(Japanese original by Satoshi Fukutomi, Kyoto Bureau)