Body & Soul4 mins ago
Evolutionary Biology
Can anyone tell me if there is ananimal that's evolution in any way has been affected by humans? By this i mean, when the creature is born, something in it's genetic structure would not be the way it is if humans hadn't impacted on it in sime way. Viruses are an example that would fit this, but i'm wondering about more complex organisms.
The only example i've heard of is some type of wood pigeon which had previously foraged on the canopy, but due to human factors the fruits there no longer existed, so the bird was forced to forage lower down. Now, even when there is abundance above, the birds still tend to look on the ground. I'm not sure on the details of this case, and how it was tested to make sure it wasn't just learned behaviour.
The only example i've heard of is some type of wood pigeon which had previously foraged on the canopy, but due to human factors the fruits there no longer existed, so the bird was forced to forage lower down. Now, even when there is abundance above, the birds still tend to look on the ground. I'm not sure on the details of this case, and how it was tested to make sure it wasn't just learned behaviour.
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As usual, dawkins, I appreciate your knowledge and clarity of explanation. Here's where I've a problem with Kettlewell: It appears (and I think you tend to confirm this, though I wouldn't put words in your mouth) that the moth had differing shades throughout its population. I mean, one could find darker and lighter shading wherevever this species of moth could be encountered and the literature I read indicates it to be fairly ubiqutious in the U.K. That said, one of Majerus' concerns was Kettlewells lack of investigation into the coloration and ratios of the larvae. It appears possible that the poulation of "wrong" shaded moths could be decimated because of increased visibility. At no time does Kettlewell infer (as far as I can see, not having read the entire project) that all of the "wrong" shaded moths disappear due to increased predation. Once the environmental causes were reversed the numbers appear to return to "normal" of both or all various shades. I think my read of your last post (first part) seems to agree that a variety of shading is found in the general population. I can't see how this can, at least for the short term, presage DNA modifications leading to permanent changes in the species. In fact, the return to 'normal' after the Clean Air Act only, in my way of thinking, indicates population shifts in numbers, since there appears to have always been some remnants of all shadings. I think this evidenced by your comment "...any variation in phenotype is reduced (emphasis mine) by predation." At any rate, thanks for your reasoned approach...
No problem clanad. You are correct, the peppered moth is not an example of speciation, they do not select mates through colour or markings. It illustrates natural selection.
Kettlewell was probably guilty of pre-empting his own results. Majerus was critical of Kettlewell's methodology and really concluded that one could not draw firm conclusions based on Kettlewell's research and that more research was necessary. There are various other studies unrelated to Kettlewell that show a correlation between moth colour and predation.
Kettlewell was probably guilty of pre-empting his own results. Majerus was critical of Kettlewell's methodology and really concluded that one could not draw firm conclusions based on Kettlewell's research and that more research was necessary. There are various other studies unrelated to Kettlewell that show a correlation between moth colour and predation.
