Night-time vision evolved millions of years ago in early mammals, a study suggests.
The photoreceptors that help us see in dim light developed from colour-detecting cone cells in Jurassic mammals, according to genetic evidence.
The evolution of night-time vision is regarded as a landmark event in the rise of mammals.
A nocturnal lifestyle allowed the first of their kind to avoid predatory dinosaurs, say scientists.
Co-researcher Dr William Ted Allison of the University of Alberta, Canada, said the development of night vision was a "critical step" in the dominance of mammals.
"We're learning how mammals evolved their vision to survive at night-time and avoid dinosaurs," he told the BBC.
"That's what allowed mammals to diversify and become abundant in the world.
"They did that by switching their daytime vision in the cones to allow night-time vision using their rods."
Rods and cones
- When light enters the eye, it ultimately reaches the retina, which is the light-sensing structure of the eye.
- The retina contains two types of photoreceptor cells, called rods and cones.
- Rods are responsible for vision at low light levels. They do not help in colour vision.
- Cones are specialised for resolving fine detail in bright light.
- Animals that are active in both day and night need to have two systems.
Genetic research published in the journal, Developmental Cell, suggests the light-sensitive rod cells in our eyes originally developed from colour-detecting cone cells millions of years ago.-read more
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