Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

Ambient light levels influence visual system size in birds and primates. Here, we argue that the same is true for humans. Light levels, in terms of both the amount of light hitting the Earth's surface and day length, decrease with increasing latitude. We demonstrate a significant positive relationship between absolute latitude and human orbital volume, an index of eyeball size. Owing to tight scaling between visual system components, this will translate into enlarged visual cortices at higher latitudes. We also show that visual acuity measured under full-daylight conditions is constant across latitudes, indicating that selection for larger visual systems has mitigated the effect of reduced ambient light levels. This provides, to our knowledge, the first support that light levels drive intraspecific variation in visual system size in the human population.

Original publication

DOI

10.1098/rsbl.2011.0570

Type

Journal article

Journal

Biol Lett

Publication Date

23/02/2012

Volume

8

Pages

90 - 93

Keywords

Body Weights and Measures, Eye, Geography, Humans, Linear Models, Orbit, Photoperiod, Selection, Genetic, Statistics, Nonparametric, Sunlight, Visual Acuity, Visual Cortex