So, I would think there is always selection, even if minimal but even if not, wouldn’t genetic drift eventually cause speciation if populations were reproductively isolated over long enough time?
Here is a better link on that topic.
Oh I see… you were focusing on the human role in creating this difference between St. Bernard and Chihuahua for some strange reason, when I was talking about the physical difficulty of these two animals of the species interbreeding.
Incorrect. We have shifted this to a matter of survival only. I have already granted that playing with words and thus making natural selection include reproductive selection muddles the issue since anything approaching speciation itself will be called reproductive selection. But when it is a matter of survival only, you will still get not only evolution but speciation as well.
All that speciation requires is a restriction on interbreeding and genetic drift will take care if the rest. To give another example, we know that variation produces various methods of increasing sexual attraction such as colorful displays and sounds. Even without survival selection these advantages will make interbreeding much more likely within certain groups and then again genetic drift will result in speciation eventually.
But then this might be considered an example of reproductive selection… sigh… As long as human language is used there will always be a philosophical/linguistic element in such discussions (very useful for ideologues for pushing their way of thinking).
Programmed cell death doesn’t seem to be involved in shoot branching, but it is central to root branching.
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Huh? That’s not even wrong.
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I’ve long suspected as much but had only anecdotal evidence to go on. Nice to at least get corroboration for my own observations.
Hmm, you’re all making excellent points. @jpm, @sfmatheson … possibly I’ve overstated my case a little, depending how exactly this thought experiment is set up. Fwiw, I’ve been picturing an environment without death (even of older generations) and without geographical barriers.
This argument confuses me greatly, because I cannot see how your “survival only” is not natural selection. Survival may not be the only type of natural selection but it is certainly one type of it!
But this is sexual selection! It is one of those different types of selection from survival selection, but I definitely did not allow for either one when I posited a world without selection. They are both forms of natural selection.
I admit I am not entirely certain of the phrase “reproductive selection,” and a minute or two of googling leaves me still uncertain.
But let me adjust my position regardless, I suppose. In a world of infinite reproduction and no death, branching trees and real speciation would never occur. But if you set up a system of non-infinite reproduction and generation-based and/or purely random death, then you would get some branching and speciation, although not nearly as much or as fast as you would with any meaningful form of selection. This has been a very interesting thought experiment!
I don’t think that’s a mistake that any evolutionary biologists are making.
It may be but needn’t be. If the population size is limited by some other factor, then predation changes the traits being selected for, but not the force of selection.
Which will produce rapid phenotypic change. I’m still not seeing an argument here for why predation is obviously nonsensical as an explanation for the Cambrian Explosion.
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It’s made up. Mitchell McKain doesn’t really know what he’s talking about.
The usual term is “sexual selection” but I think “reproductive selection” is a better more general term including the same things. After all, plenty of oranisms reproduce by asexual means and things which limit asexual reproduction for those organisms would also be a type of natural selection and surely you can see this is similar enough to sexual selection to be in the same category. So reproductive selection is a rather obvious extension and it astounds me that you people are that rigid and hidebound.
Since you don’t know me Mr. Matheson, you DEFINITELY don’t know what you are talking about. I am a physicist not a biologist, to be sure, but if terminology like this is such a problem for those in the field, then biology is a much much softer science than I previously thought.
I’m afraid this make no sense to me. Sexual selection refers specifically to selection involving competition for or choice of a mate. I see nothing similar about selection in asexual organisms.
It may be obvious to you, but I still don’t know what you mean by the term.
Your argument is that biology is a soft science because it’s too rigid in its terminology – not like loosey goosey physics? As someone who’s been both a physicist and a biologist, I am gobsmacked.
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Clearly anything which limits or interferes with reproduction is going to limit an organisms contribution to the gene pool. FRANKLY, it is this inability I am seeing here to go beyond what you can look up in wikipedia which tells me that it is you people are the ones you don’t know what you are talking about.
What is important in physics is the mathematical description. Physics has very precise mathematical definitions of terms. But no I don’t see physicist getting so uptight about using a more general term for something in an English description. It is done all the time. So I think this supposed “gobsmacking” is a put on, until I hear a comparable example from physics.
Amazingly, sexual selection is nicely described and defined in Wikipedia. And in the dictionary. And in textbooks. And websites.
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