Biology Letters
Restricted accessEvolutionary biology

Bare skin, blood and the evolution of primate colour vision

Mark A Changizi

Mark A Changizi

Sloan-Swartz Center for Theoretical Neurobiology, California Institute of BiologyMC 139-74, Caltech, Pasadena CA 91125, USA

[email protected] [email protected]

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,
Qiong Zhang

Qiong Zhang

Division of Biology, Computation and Neural SystemsMC 139-74, Caltech, Pasadena CA 91125, USA

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and
Shinsuke Shimojo

Shinsuke Shimojo

Division of Biology, Computation and Neural SystemsMC 139-74, Caltech, Pasadena CA 91125, USA

JST ERATO Shimojo Implicit Brain Function Project, California Institute of TechnologyMC 139-75, Pasadena CA 91125, USA

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Published:https://doi.org/10.1098/rsbl.2006.0440

    We investigate the hypothesis that colour vision in primates was selected for discriminating the spectral modulations on the skin of conspecifics, presumably for the purpose of discriminating emotional states, socio-sexual signals and threat displays. Here we show that, consistent with this hypothesis, there are two dimensions of skin spectral modulations, and trichromats but not dichromats are sensitive to each. Furthermore, the M and L cone maximum sensitivities for routine trichromats are optimized for discriminating variations in blood oxygen saturation, one of the two blood-related dimensions determining skin reflectance. We also show that, consistent with the hypothesis, trichromat primates tend to be bare faced.

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