Posted by rpcman on April 27, 1998 at 14:05:43:
In Reply to: How about this experiment... posted by Walker on April 27, 1998 at 13:18:49:
: This is the kind of thing I am looking for, except this experiement would only demonstrate selection on an e existing trait, not evolution as I understand it. Correct me if I'm wrong but the peppered moth, of whatever color is still a peppered moth (the same species).
Yes it is the same species. There are numerous species which have been witnessed to evolve into separate species. Although I don't know of an instance off the top of my head, I'm sure new species have been evolved in the labratory. The problem is that this is artificial rather than natural. Mutation rates are far to low (and unpredictable) to 'naturally' experiment with creating new species. However, mutation rates are very predictable in terms of raw numbers at the molecular level (what the specific mutations will be is the difficult part). Again, see the textbook Evolution for specific details on the predictable rates of mutations.
: I propose something different: Pick some species with a known gene set. If we choose some bacteria then we have the benefit of rapid reproduction plus asexual reproduction enures the same gene set for the entire group (This way we can catalog the gene set of just one cell rather than every cell in the sample and mutations will be easier to track) Now just take that one cell and have it reproduce several times.
: Note: I am not a biologist so maybe using a single set of genes would somehow invalidate the experiment, you tell me.
I'm not a biologist (or even a professional scientist) either. Chris can probably help out on these kinds of details.
: We should control it's environment as much as possible, temperature, food source, radiation, etc. Now let's add a stress factor such as an anti-biotic. Watch the bacteria for many generations until it mutates a gene(s) that give it resisistance. Repeat this experiment several times to see how often the same set of mutant genes crop up. (That way we know our mutation isn't just a one time aberation)
: Surely, someone has tried an experiement like this. Please let me know if you have come across something like this in your reading (not just selection of an existing trait) I certainly would want to read about the experience of others before I set out to do this in my kitchen on my own time.
I'm sure this has been done countless times although I don't have a reference. There is a journal that publishes these kinds of studies. I'll get the name for you one of these days.
: Can't we set up the conditions for such a mutation again and watch it happen over and over?
I don't think the same mutations can be produced over and over again even if radiation or some other agent is used. As Stephen J. Gould states, if we were to rewind time back billions of years and started the process all over again, we wouldn't end up with the same mix of life that we have now. Think about it. A single freak accident or weather change a billion years ago (not to mention the meteor that wiped out the dinosaurs and caused the flourishment of mammals) could significantly effect the life we currently see.
: Document a prediction that was made about vaccines or pesticides in terms of how the target organism would evolve (not shift existing traits) to defeat said vaccine or pesticide. I grant you, gene shift happens, natural selection of traits happens. These aren't evolution. Evolution means a new (successful) gene pops up.
See Evolution for much discussion on this. I don't have it with me here at work.
: Yes, a theory is more than an untested, or unobserved hypothesis. I'm not certain evolution has been tested sufficiently to be considered fact.
Here is where we disagree. I think you may just need to read more of the research--especially from the past couple decades.
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