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Is short-sightedness found in other animals? Did it also affect ancient humans? (continued)
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Peter Bursztyn
Barrie, Ontario, Canada
I am not sure how one could determine whether a wolf, an eland or a cheetah were short-sighted. I can鈥檛 imagine devising something like an optometrist鈥檚 eye chart for animals.
Moreover, if a solitary hunter like a leopard were myopic, its success in locating prey would be compromised and they wouldn鈥檛 thrive. In the case of social hunters like African wild dogs, a myopic animal might survive by sharing the prey brought down by others.
Infant-directed speech is characterised by a slower, more deliberate way of speaking, with long, drawn-out syllables
The problem is serious for solitary prey animals. If such an animal can鈥檛 see well, a predator is able to approach closely before pouncing. The issue is less acute for prey animals travelling in herds. Members of the group with sharper vision can be relied upon to sound the alarm. This is probably why the great majority of animals, predators and prey, live in groups.
For humans, the issue is more nuanced. I have thought about this off and on for decades, because my right eye is very myopic and requires more than twice the correction that my left eye needs. This condition is clearly hereditary: my brother has the same pattern of myopia, as did our father. It appears confined to the male line because my daughters don鈥檛 need corrective lenses at all. Myopia would have died out entirely unless it 鈥� at the bare minimum 鈥� didn鈥檛 greatly disadvantage humans with the condition.
First of all, humans are rarely solitary. In a hunter-gatherer society, a myopic individual would simply avoid hunting. On the other hand, myopia would have to be severe to impede the gathering of fungi, nuts, fruit or nutritious vegetation.
As societies became more advanced, opportunities would appear for myopic members to specialise in tasks benefiting from acute close vision. Some examples would be stone knapping (making stone tools), grooming (locating lice and other parasites), wood carving and jewellery crafting.
I would suggest that myopia did affect ancient humans. However, they likely found it useful. Had it not been, 鈥渟urvival of the fittest鈥� would have eliminated the trait.
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