Ophthalmology

Ask Mr Brain...all will be exoplained

PUBLISHED : Thursday, 29 July, 1999, 12:00am
UPDATED : Thursday, 29 July, 1999, 12:00am

How come some people can roll their tongues and others cannot? This is because being able to roll your tongue is controlled by a gene. If you have the gene for tongue-rolling then you will be able to roll your tongue, otherwise, you will not.


Why are humans getting more and more clever but other animals are not? CRYSTAL LOK Although our scientific and technological knowledge is growing at a rate undreamed of last century, humans are not any more intelligent than they were 100,000 years ago. As it is we only use a fraction of our huge brains in our everyday life. Unless there was some bizarre catastrophe - which for some reason only the most intelligent people were able to survive - there is unlikely to be any evolutionary pressure on man to become more intelligent.


Other animals, however, are a different matter. For example, the faster an antelope can run, the more likely it is to escape from predators such as lions. The faster antelopes are thus more likely to live long enough to breed, passing on their speedy genes to their offspring. Eventually all the antelopes will be fast runners, but that will not save them from being eaten. While the antelopes have been evolving to be faster runners, the faster lions have been more successful at hunting antelopes and pass on their speedy genes to their offspring, while the slower lions are less likely to survive and breed.


The upshot is that if one species evolves to become faster than its predators, you can be sure the predators are also evolving to run faster so as to catch their fleeter-footed prey.


So despite thousands of years of genetic variations being 'selected' to ensure greater speed, they effectively end up back at square one. Biologists call this the 'Red Queen', after the character Alice met in Lewis Carroll's Through the Looking Glass and What Alice Found There. In that magical land, because the landscape moved, the Red Queen and her court had to keep running just to stay on the same spot. This is effectively what is happening with predators and their prey.


Because humans are able to change the world around them, there is little evolutionary pressure on them. When conditions change and a new problem emerges, man uses his large brain to come up with new technology to overcome the problem, rather than being geneti cally 'selected' to cope with the new conditions.


When man moved out of Africa into the cold northern climate, he did not evolve into a hairy man. Instead he killed hairy animals and used their skins to keep himself warm.


What is achromatopsia? Achromatopsia is a rare inherited vision disorder. Normal people have both cones and rods in their eyes to help them see. People who suffer from achromatopsia do not have cone vision and so rely entirely on rods.


In bright conditions, the rods become saturated and so do not provide colour vision or good detailed vision. Therefore achromats are either totally or almost totally colour blind.