Part of the show Science Question and Answer - New Horizons Mission
Kane via email asked:
Is it true that some of our senses degenerate and that some of them are more susceptible to damage than others? We see kids wearing glasses but we don't need to use hearing aids until we're very old. What's going on?
With glasses, there's definitely some kind of environmental effect there. If you spend all your life studying, then you're much more likely to end up with short sightedness. I can see that both Phil and I have glasses on today! In Singapore where there's a very strong emphasis on education from a very early age and lots of people spend lots of time studying, the rates of short sightedness have gone through the roof. There's a lot to be said for people going out onto the sports field and learning to focus their vision in the distance. When you're young and you're body is developing and growing, if you do a lot of close work you don't develop a capacity to see well into the distance. But in terms of degeneration, just because you wear glasses doesn't mean that your eyes are actually degenerating; it just means that they're not working as effectively as they could. With going deaf, on the other hand, there's actually a problem with part of the ear that turns sound waves into electrical signals. That's because over time the tiny nerve cells that do that job get damaged by loud noises, the effects of ageing and the effects of damaging chemicals in the blood stream. Once they're lost, you can't replace them, which is why you get a progressive deafness.