QUOTE(Leonardo @ Dec 9 2006, 01:21 AM) [snapback]1456076[/snapback]
boorite,
Please read the article in this
link.
It's a good article. What it says about how new species of humans might or might not arise is precisely what I'm getting at.
QUOTE
It is possible we can create the conditions which may require us to 'evolve' unnaturally.
Exactly. Un-natural selection. What I called "artificial selection."
QUOTE
Of course you first must accept that human behaviour, through our use of technology, can affect the environmental conditions of Earth on a global scale. But, once you accept that, you find we can cause this 'stress' I speak of - and the result could be a forcible adaptation to the new environment (or a creation of a 'bubble' environment suitable for our existence without adaptation).
No, that's not quite right. A changed environment does not force adaptation, resulting in speciation. ("Adaptation," again, is a deprecated concept and a very strained metaphor for evolution by natural selection, for reasons we can go into if you like.) At most, a novel environment
selects for different traits from the ones selected for in the previous environment. What is necessary is
selection, i.e., something in the environment must change the probability that a given gene will be copied-- or that an individual with a given trait will produce offspring capable of reproduction, if you prefer. The chances of this occurring in a contemporary human population are vanishingly low. That's one of the things the author of your article points out, citing Mayr.
QUOTE
I did not say we are currently evolving (although the gene change mentioned in the above link indicates we may be), I said we are still subject to the forces of evolution. Where was the 'technical problem' with that statement? If you wish to assume I said we are evolving then you assume incorrectly.
I don't assume that. I tried to make two of the difficulties clear in my previous message. If it's still not clear, it's not worth going on about, because we're startlingly close to agreeing.
QUOTE
I do understand the context in which Darwin formulated his theory of evolution, I can simply think beyond a species or two on an island (or a few islands) and apply this theory to other situations.
Apply the theory, then, to the question of speciation in contemporary humans. What are the main variables governing speciation rates? What are the values of those variables in any technologically advanced human population?
The upshot of the article you linked (as it bears on this thread) is that evolution of a new human species by natural selection is very unlikely. If a new species of humans arises, it will be through
artificial manipulation of the genome-- "unnaturally," exactly as you say-- not through straightforward Darwinian processes.
Which is all I'm saying.
Edit: I'm wondering what your background in evolutionary theory is, where you came by your idea of it, what it means to you, that kind of thing. Have you read Mayr, for example? Do any particular writers or theorists spring to your mind when you think of evolutionary theory post-Darwin? If I know where you're coming from theoretically, I might not have so much difficulty making sense of what you're trying to tell me.
Edit 2: Note that the author of your article is not a biologist. It's still a good article, and he does cite Mayr. It is, however, what it is, which is a highly speculative article by a non-biologist. The best way to get hold of evolutionary theory is to read Mayr himself or other working research biologists. Just a suggestion. Still, a thought-provoking article, so thanks.