A question concerning EVOLUTION that I don't understand

[seasnake]

The thing I don't understand about evolution is how if at one time on Earth no creature had eyes to see with, how so many species today have eyes and eye sight. If many isn't related to several, if not most, of the pre-historic man/ape like species you would also expect that man isn't related to most of the pre-historic non-man/ape like creatures as well, and this would go for all the other species not being related to each other as well in terms of passing down changes and mistakes in DNA resulting in eyes and vision.

What puzzles me even more is the statistical likelihood of different species of creatures developing the same innovations like eyes, ears, same number limbs for mobility, and so forth. Perhaps the eye-vision system was like some sort of ancient disease, get bit by a certain type of misquito or bug, or on an ifected newt, and you and your offspring come down with a bad case of having eyes.

 

[MATLABdude]

The thinking is that eyes started out as photoreceptor cells, or even a photosensitive vacuoles (phytochromes) within single-celled organisms. These would have come in handy when trying to avoid predators, or find prey, as they blocked out light, or in moving towards sources of light (for organisms capable of photosynthesis). Specialization and refinement into what we know as eyes would have then come via evolution / selection.

The Wikipedia article may be a good starting point (especially since I'm not a biologist):
http://en.wikipedia.org/wiki/Evolution_of_the_eye

 

[russ_watters]

What puzzles me even more is the statistical likelihood of different species of creatures developing the same innovations like eyes, ears, same number limbs for mobility, and so forth. Perhaps the eye-vision system was like some sort of ancient disease, get bit by a certain type of misquito or bug, or on an ifected newt, and you and your offspring come down with a bad case of having eyes.

The odds of winning the lottery are pretty bad (so bad, no one should ever do it), but if you play the lottery every day for 3 billion years, you'll actually win quite a few times!

The thing I don't understand about evolution is how if at one time on Earth no creature had eyes to see with, how so many species today have eyes and eye sight. If many isn't related to several, if not most, of the pre-historic man/ape like species you would also expect that man isn't related to most of the pre-historic non-man/ape like creatures as well, and this would go for all the other species not being related to each other as well in terms of passing down changes and mistakes in DNA resulting in eyes and vision.

I'm not sure what you mean there - having eyes and being able to see is an advantage, so most animals would keep mutations that improve their eyesight. Evolution is not, strictly speaking, a random thing, it is directed by a sort of pressure to survive and propagate.

 

[arildno]

seasnake:

Natural selection works locally, bith in a spatial and temporal sense.

THat means that at every point where some mutation outcompetes another mutation, then the theory of natural selection DEMANDS that there must have been some advantage of the winning mutation relative to the loser.

If it COULD be proven in some case, that the winning mutation in a statistically significant population actually ONLY had disadvantages relative to the losing mutation, then the theory of evolution would have been proved wrong.