Extracts & Author’s Conclusion
- Old World monkeys and apes (called catarrhines) evolved trichromacy: red-, green- and blue-colour vision. Most other mammals have two diﬀerent types of colour photoreceptors (cones) in their eyes, but the catarrhine ancestor experienced a gene duplication, which created three diﬀerent genes for colour vision. Each of these now codes for a photoreceptor that can detect diﬀerent wavelengths of light: one at short wavelengths (blue), one at medium wavelengths (green), and one at long wavelengths (red). And so the story goes our ancestors evolved forward-facing eyes and trichromatic colour vision – and we’ve never looked back.
- Our own vision does not have this even spectral spacing (Note1). In humans and other catarrhines, the red and green cones largely overlap. This means that we prioritise distinguishing a few types of colours really well – speciﬁcally, red and green – at the expense of being able to see as many colours as we possibly might. This is peculiar. Why do we prioritise diﬀerentiating red from green?
- It is still not known exactly why humans have such strange colour vision. It could be due to foraging, social signalling, evolutionary constraint – or some other explanation. However, there are many tools to investigate the question, such as genetic sequencing of an individual’s colour vision, experimental simulation of diﬀerent colour vision types combined with behavioural performance testing, and observations of wild primates that see diﬀerent colours.
- There’s something strange about the way we see colours. We have prioritised distinguishing a few types of colours really well, at the expense of being able to see as many colours as we possibly might. One day, we hope to know why.
See Aeon: Higham - The red and green specialists: why human colour vision is so odd
Footnote 1: Unlike bees and digital cameras.
Text Colour Conventions (see disclaimer)
- Blue: Text by me; © Theo Todman, 2019
- Mauve: Text by correspondent(s) or other author(s); © the author(s)