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Medaka as a tool for studying human diversity and evolution

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Posted January 22, 2015

Variations in appearance (such as eye color, hair color, facial features, among others) are observed in worldwide human populations. However, there also exists geographical variation in sexual differences, such as body size, often referred to as sexual dimorphism in the literature. In general, sexual differences among human Asian groups are smaller than that of African or European populations. However, the molecular evolutionary mechanisms of these differences are still relatively unknown.

Outdoor breeding facility that keeps medaka geographical populations, in Kashiwa campus, the University of Tokyo. © 2015 Takafumi Katsumura.

Outdoor breeding facility that keeps medaka geographical populations, in Kashiwa campus, the University of Tokyo. © 2015 Takafumi Katsumura.

In this study, a collaborative research group of Professor Hiroshi Mitani, Professor Shoji Kawamura, Professor Hiroshi Kataoka and Associate Professor Shoji Oda at the University of Tokyo Graduate School of Frontier Sciences Department of Integrated Biosciences, Associate Professor Hiroki Oota and Doctoral Researcher Takafumi Katsumura of Kitasato University School of Medicine Department of Anatomy, and the Institute of Statistical Mathematics found evidence for a genetic variation in an enzyme involved in drug metabolism in medaka fish that affected the degree of sexual differences in local geographic groups, as observed using wild medaka populations in Japan. This result indicates that geographical differences in sexual variation have been built upon a trade-off between drug metabolism for individual survival and mate choice for reproduction that have been acted on by “natural selection” and “sexual selection” originally proposed by Charles Darwin.

Further, since genetic variation in this same drug metabolism enzyme and geographical sexual dimorphism similar to medaka is also seen in humans, it suggests that geographical differences in sexual variation may also exist in humans based on a similar evolutionary trade-off.

This research paper was published in the British journal “Proceedings of the Royal Society B: Biological Sciences”.

Source: University of Tokyo

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