Colour Vision
Origins of Us - Guts
Most mammals wouldn't be able to tell the difference between the two tomatoes. But for you and me the difference is obvious, one is red and one is green, and this is all because of a crucial change in our ancestor's eyes that probably happened 30 to 40 million years ago.
At the back of all mammals eyes are light sensitive colour receptors called cones. Most mammals only have two types, that cover the blue and yellow parts of the spectrum. But 30 million years ago, a genetic mutation created a third, one that opened up a whole new range of colour - reds and greens. And, with this our full colour vision was born, resealing a rich and bountiful range of foods.
If you're a leaf-eating primate, three colour receptors might help you pick out the slightly paler, more yellow, tender leaves to eat. But for a fruit eating primate, it means you can pick up on the signals that the trees are giving you, that when something is ready to eat it turns red and you know that it is full of sugar and more nutritious.
Being able to tell when fruit was ripe, packed with life-giving sugar and energy, must've been a massive advantage in our ancestors struggle for survival.
Those animals with eyes tuned in to finding the richest foods were more likely to survive and pass on their genes. and so colour vision spread until their descendants, including us, were seeing in glorious Technicolor.
With our three types of colour receptors, our eyes can see up to a million different colours. Our colour vision is a sensory gift. There are relatively few other mammals that see all the rich and varied colours that we do. And that goes all the way back to our monkey ancestors searching out the most tender leaves, the ripest fruits in those forests 30 million years ago.
