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Author Topic:   Ring Species!!
NosyNed
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Posts: 8996
From: Canada
Joined: 04-04-2003


Message 3 of 50 (503092)
03-15-2009 11:28 PM
Reply to: Message 1 by harry
03-15-2009 9:15 PM


Time Rings
In Question about evolution, genetic bottlenecks, and inbreeding you have questions that might be explained if you think of evolution of new species as being like ring species in time instead of space.
Does that make any sense to you?

This message is a reply to:
 Message 1 by harry, posted 03-15-2009 9:15 PM harry has replied

Replies to this message:
 Message 4 by harry, posted 03-16-2009 6:54 AM NosyNed has replied

  
NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 6 of 50 (503140)
03-16-2009 10:58 AM
Reply to: Message 4 by harry
03-16-2009 6:54 AM


Re: Time Rings
No it does not because i don't think evolution happens in space instead of time.
Evolution obviously happens in time.
In the case of the ring species we see there are a series of populations separated by geography with some limitation on gene flow between them. You can visualize an original population gradually spreading out over some areas generation by generation. The individuals further from the source will have less gene flow back to that source and will have diverged farther from it.
If we look at a population over time (let's use humans as an example) we get a similar situation. One hundred generations ago was the time of the ancient Egyptians. It is pretty darned sure that we could interbreed with them but time separates us so there is no gene flow just like geography can reduce (or stop) gene flow.
If we go back 1,000 generations we are in the stone age and there are genetic differences between us and them but we could still (probably) interbreed with them. If we go back 2,000 generations that population could certainly interbreed with the population 1,000 generations in our past. So could we probably but there will be more genetic differences. This continues in time.
At about 10,000 generations back we have a population that could certainly interbreed with the population from 9,000 generations back. However, that population (10k gens back) is probably no longer our own species. (Though interbreeding might be possibly successful we probably (most of us ) wouldn't want to try so speciation has happened).
If we go back 100,000 generations we have a population that certainly could interbreed with the population 99,000 generations back and for many though (say) about 70,000 gens or closer. However, there is a very good chance that (100kgens) population could not interbreed with us and we would be about as interested as we would be in a chimp.
This gradation in changes that never produces a sharp line of speciation anywhere over the many thousands of generations is exactly the same as the gradual change you see over geography in the case of ring species. There is not sharp line that marks a species boundary but at the extremes there are two different species.
Surely being able to view how species A got to species B by looking at the species that they were in between points A and B is nothing to do with space just because they didnt die off.
I don't understand this at all. Please explain.

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