One for the evolutionists - The humble crayfish hasn't changed for millions (or billions ((however long you

Question

beileve)) of years. All the fossils found show this. Why is this so?

Answer 1

Because it's current structure has allowed it to survive through different conditions over the years. If there's no natural selection at work, then there isn't going to be too much visible evolution (not that natural selection is the only component; there's also genetic drift and a few other factors; but it drives a lot of it).

Not surprisingly, when we look at environments that haven't really changed in a long time, such as the very deep ocean, we find some examples of organisms (such as horseshoe crabs) that haven't changed.

If you think that evolution is the implication that species will always change over time, following a pre-determined chain of "higher" organisms, you'd be wrong.

http://www.talkorigins.org/indexcc/CB/CB930.html
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Answer 2

There have been some changes, but they have been pretty minor. Crayfish occupy a pretty narrow niche in the environment. The selection pressure is pretty extreme. No matter how much gene shuffling they do it is pretty difficult for them to cast off their shells (yes, I know it is a bad turn of a phrase). If they did not have such severe restrictions on them they would likely show more changes. If you look at it another way (and somebody should have by now) they might be the source for a lot of other similar creatures like lobsters or crabs instead of being descended from the salt water species.

Anyway they are not quite as stable regarding evolutionary change as you seem to believe. Most of the fossil species of crayfish are definitely extinct.

Answer 3

No. You are lying. There are ~500 species of crayfish today. And a variety of fossil crayfish going back over 200 million years. These are NOT the same species as the living crayfish. They HAVE changed.

Answer 4

it doesn't need to change - I dont think sharks have changed much either

evolution is about being best adapted to survive long enough to procreate in which ever environment you are in. Obviously crayfish are having no problems

people who ask biology questions in R & S are cowards

Answer 5

Because it's well suited to its environment already, and that environment hasn't changed much in that time.

That's an easy one.

Now, I suspect that you thought that this was a challenge to evolution, because (I suspect) you thought that evolution is a matter of beings simply "improving" over time: the "evolution is progressive" fallacy that leaves us with all of this "so why has man stopped evolving" and "mutations can't increase information" nonsense.

Answer 6

It fills it's ecological niche perfectly.

The duration between the oldest fossilized crayfish and the present day is not a matter of belief.

Maybe post this in the Biology section.

Have a nice day.

Answer 7

Because the design works, and there's no advantage in anything different. So mutants don't out-breed the normals.

Tell ya what, though, I bet there are internal changes you can's see that reflect changes in ocean temperature, oxygen content and other subtle environmental changes.

CD

Answer 8

Steamed Crayfish in Hollandaise Sauce is a fantastic dish...ummm,...yummy!!

Answer 9

There was no need for it to evolve. The cockroach, the crocodile, and many other creatures havn't changed as well.

Answer 10

If it ain't broke, there's no reason for natural selection to fix it. Only mutations that enhance the ability to survive and reproduce are selected. If there's no room for improvement within the organism's basic layout, nothing will change.