Asked by: Mark Buckmaster, Leicester
Vision defects such as myopia (short-sightedness) aren’t caused by just one single gene. There’s some evidence that short-sighted people have a higher than average IQ, which may be because the same genes affect the eyes and brain. Vision defects often have environmental causes as well. Myopia is more common in people who do a lot of close-up work, have saturated fat in their diet and sleep with a light on. These are all relatively new in our evolutionary history.