Why are tpeople still born with bad eyesight?

Question

Why are there people still born with bad eyesight?
Isn't it evolutionary seen a bad gene to reproduce?
Wouldn't such a bad-physical trait be extinct by now if only the strong survive?

OK. so alot of people say it's because people with bad eyesight get aids to help them.
Though, bad eyesight isnt something 'New'
or just from the 20th century I presume????

Or did they have glasses and contacts in the time BC?
Or even when we used to live in tipi-like homes?

How did bad eyesight survive al of that?

Answer 1

some eye problems are genetic,,,,, so since we have visual aids, glasses and contacts,,,,, no there isnt any reason that evolution would diminish the gene pool of those with this condition,,,,,, if we didnt have visual aids,,, these people might be considered less attractive, or have more accidents etc,,,,,, and thus not reproduce as much and then keep passing on that gene
its like diabeties (some forms) and heart disease, people use to just waste away from it,, only not often before they reproduced, so the tendency for both never got eliminated from the gene pool, and now we have treatments,

Answer 2

Humans are a social animal and solidarity is also a trait resulting of evolution. Blind people or people with bad eye-sight can be good and useful at many things if helped a little.

And evolution has not suppressed all inherited diseases, far from it! The reason is that many gene defects are recessive, meaning that if one get a functional copy of the gene from one parent and a defective one from the other parent, the functional copy compensates the defective one. Only if one gets two defective copies of the same gene does one get the defect causing the disease. See for example diabetes (type I) or haemophilia: these diseases have always been around, and patients used to die very early. Now they can be managed, but they have not disappeared.

Answer 3

Civilisation has lasted such a short time that there has barely been any opportunity for evolution to work on us - so you have to look back to pre-history.

How much of a disadvantage would poor eyesight have been to a caveman or nomadic hunter-gatherer? It all depends how poor, of course - slightly long-sighted not a problem, totally blind a major setback. But it also depends on the functions that person might fulfil - for instance, short sight would have been more of a disadvantage to a man hunting than a woman caring for children. But also in prehistoric society there was a role which the blind could fulfil, often more capably than their sighted brethren, of "oral historian" (think Homer, but they are also known in the Chinese tradition) which carried considerable status and would have enabled them to reproduce.

Also, remember that a lot of birth defects are either due to first-generation mutations (ie ones which occur spontaneously in the current generation), or are not down to faulty genes at all: they may be caused by, for example, maternal exposure to certain toxins such as dioxins.

Answer 4

The reason is because of natural selection - thats not whats happening to humanity right now. I wear glasses but you know what? My bad eyesight has not resulted in not seeing a sabretooth tiger at a crucial moment - I'm alive and I may replicate my dna too (thats not how my girl would like it described but there you go) selection pressures are eased in us. It could be argued that its just genetic drift.

The truth is not only the strong survive. Not in a civilised society with medicine and law.

Answer 5

It depends. Babies actually have terrible sight (about 20/200), but the eye then gradually changes and grants them good sight. In most cases. Some people have been myopic their entire lives. Most myopia (and the opposite of myopia, hyperopia, or long sightness) occurs in roughly school age and highschool age (such was the case with me). Eyesight stops changing at about age 21 (although it never stops changing with some people). Then, at the age of 40, the crystalline lens loses it elasticity, progressively diminishing the person's ability to focus up close, making people need reading glasses. This happens to everyone, as it is a normal process of aging, like white hair and wrinkled skin.

Answer 6

Yes it probably would be a non-existent trait if it was a matter of just the strong surviving. But because it's not just that the strong that survive like in the animal kingdom, we get weaker, not stronger.

We have medicines, surgery and machines all keeping alive the weak that would have died in a naturally balanced world of survival of the fitness. This keeps the gene pool to diverse and open and preventing us from becoming impervious naturally to disease and disabilities.

Answer 7

Some traits change through evolution if they lower the chance of survival - in the modern world it doesn't affect our survival as we can just wear glasses etc. in cavemen times most people would have had good eyesight as it would have increased their ability to spot danger. Over time as humans have adapted, mutations have evolved but they are only mutations which don't reduce survival ability.

Answer 8

First, you have to consider that deleterious mutations (i.e. changes in our genes that cause disadvantages) are repeated over and over every generation. Natural selection can prevent them from being inherited to the next generation but it cannot prevent it to appear over and over in every generation.

Second you have to consider that natural selection only acts against features that reduce fitness (i.e. an organism's capacity to bear children). So bad sight would only be under selection (and disappear from human race) if people with bad sight had less children than people with good sight.

The main issue here is that humans stopped being under Natural Selection long ago, when civilization started. Right now with the development of medicine, all deleterious mutations can pass on to the next generation because they have become treatable diseases.

Answer 9

If we didn't have optometrists, we would probably be extinct. But we do, so we're not.

If we didn't have contact lenses but all had to go around wearing only glasses, there might be a small chance that we'd be outbred by those without glasses because most people tend to find people with glasses less attractive (generally, I said). But it would take a LONG time for us to disappear.

Answer 10

If the mother carrying the baby drinks whilst she is pregnant, this can lead to the baby with many physiological disorders such as a cleft lip, slow growth rate, and poor eye site. Just one reason.