Fish developing legs to evolve would've been a freak thing, could any "birth defects" nowadays be evolution?

Answer 1

This depends on the type of birth defect you are talking about. Obviously, defected reproductive organs aren't going to go much farther in the population. However, let's expand the view, and assume that this defect leaves reproduction intact; in this case, this person would ideally pass on their defected gene.

In order for the defected gene to pass on (and therefore propagate through the population), it must attract the opposite sex. If the defect is distasteful to everyone, no one is likely to produce children with this person.

Secondly, for this to be evolutionarily advantageous, this birth defect must have a greater benefit than a cost. As a side note, for animals, this means that it must encourage survival.

Thirdly, this birth defect must be able to pass on genetically onto the next generation, and the next generation after that. There are probably birth defects that aren't necessarily genetic.

Hope that helps. =)

Answer 2

Actually, yes.

You have realised the basic tool of adaptive change. Inheritable genetic mutation.
Most birth defects are lethal, and may result in loss of the fetus before birth. Some result in deformity or retardation. Some result in no problems with the child either way, good or bad. But some may lead to an improvement in survival which will be passed on to any children and so on. Even if such mutations are caused by environmental factors, such as pollution, radiation etc, this is an adaptive stress. For all we know this could be how future generations become more resistant to higher levels of radiation. As radiation levels rise, those with an innate resistance will survive and have children, who may also carry that resistance. They will look the same, act the same and be perfectly normal, but they will suffer less from things like radiation induced cancers, leukemia etc. Small improvements, over many, many years. That is evolution.
You can safely ignore those who preach that evolution is a lie because no-one has seen a monkey change into a human, since no-one has seen anyone being created either (births don't count).

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Answer 3

The biggest "missing link" to evolution theory is a mechanism which would alter the expression of genetic material based on the experience of an individual. As an example, how is a child's skin color at birth determined based on the experience of his or her ancestors? Exposure to the sun darkens the skin as a defense mechanism. How does that experience affect the skin color of the offspring? Skin colors are estimated to have emerged less than 20,000 years ago. Lactose tolerance on the other hand is an even more recent development and is attributed to being a beneficial mutation. Yet if mutations (birth defects) and natural selection were the only sources of change, then the process would take too long to account for the adaptive diversity we see today. This is not to 'nay say' evolution, but only that we do not understand the internal mechanisms involved in it's expression. Unless some unique advantage is gained (like being the first guy on the block who doesn't get sick from drinking from a cow's teet!), mutations can account only for specific leaps in evolution, but cannot stand as a guiding mechanism.

Remember, unique advantage is a must. Good Luck!

Answer 4

Most birth defects are no beneficial. When the birth defect is severe enough the person dies. For genes to be passed on the person must live long enough to reproduce, and that still does not garauntee that the gene will be passed on to the offspring.

And even if the gene is passed on that doesn't mean it will express itself in the offspring....and if it does, it may not be to the same degree.

There are a small number of people in the world who are immune to HIV. Some of them are of British ancestry. These people decend from the inhabitants of a particular village which was ravaged by some sort of plague for a number of years, a few hundred years ago. Some of the villagers fell ill and died, some of them fell ill but didn't die, and some of them never fell ill. The ones who survived produced these HIV resistant decendants. These people have a mutation which leaves tem without docking sites for the HIV virus to bind to, and as a result, the virus cannot infect their cells to continue it's life cycle. These people may also be immune to smallpox.

This has proven to be a fairly benificial mutation. Of course most people don't have this mutation so be safe.

Answer 5

If the "defect" offered some sort of advantage to its owner at the time of its birth then it has a chance of being more successful than those who do not have it and therefore the genes that caused it have a better chance of passing on to new generations. Some birth defects crop up due to mutations that happened in sperm or eggs of the parents. Others crop up repeatedly because of recessive genes in the population. Generally they no effect or an adverse affect on the individual which is why we call them defects. But if the environment changes then what may have been neutral or disadvantageous might become advantageous and those individuals may begin to prosper and have better reproductive success than "normals". In the human population it is getting harder for that process to work because our medical and social support system cares for the less able. At the same time there is less need for new traits because we are responding to changes with technology.

Answer 6

It could be so long as the birth defect gave the person with the defect some advantage over others and they were able to pass on the defect. Most defects are a result of an error in the genetic code and do not get passed on.

Answer 7

Fish wouldn't develop legs right off (not like dad and mom have none and all of sudden their baby has them).

There are two theories about evolution - gradual and spontaneous.

For example, feathers grew on arms of animals to aid them catch insects, and ones with more feathers got more insects and therefore survived, and eventually their arms were all feathers (wings) and ones that could glide and then fly could catch insects better..... the evolution of birds. This could be seen as gradual.

If wings were to 'suddenly' appear on an animal that would be considered spontaneous, such as what you're referring to as a 'birth defect'.

Common thinking of most is gradual evolution, but with brief stints of spontaneous evolution based on environmental pressure.

Answer 8

There is no evidence that the appearance of legs was sudden. It may have been a slight advantage for longer fins before anything resembling a leg forms.

Many birth defects are not related to genetics, but rather, interruptions of the developmental sequence due to environment factors. These are not heritable.

Answer 9

Mutagenesis and the subsequent adaptation of the organism to suplant the original parent is one theory of evolution. See "Ever since Darwin" and "in the Beak of the Finch". It is what makes good science fiction "The Food of the Gods" and it is not far fetched to believe that such defects have been part of our evolutionary path.

Answer 10

No..you said the magic word "develope", that takes time. We ARE evolving,slowly....birth defects are sudden mutations brought on by cellular irregularities caused by defects in growth caused by outside effects:ie,medicines,pollutants & disease