What are the limits to so-called "micro-evolution"

[QED]

As a mechanism, natural selection does appear to work on a small scale (i.e., at the level of microevolution or special evolution). What Darwin desperately needed was a way to prove that such a mechanism could work on a large scale (i.e., at the level of macroevolution or general evolution). Despite modern refinements, this fundamental problem persists because it strikes most people as being profoundly contrary to common sense. Our experience suggests that cows have baby cows, cats have baby cats, dogs have baby dogs, etc. Selective breeding of such domesticated species shows a capacity for deriving dramatic new varieties within a few generations. Careful observations of wild populations occasionally reveal hybrid species. A wider cast of the net may catch a new species in the process of becoming reproductively isolated from its known relatives. But it is quite a different matter to say that we, along with cows, cats, and dogs, all are descended from slime.

So, the answer to this question is that modern evolutionists continue to assert that observed small-scale changes may be translated into supposed large-scale changes over long periods of time.

I can see no intellectual merit in the conclusion that "it is quite a different matter to say that we, along with cows, cats, and dogs, all are descended from slime" just "because it strikes most people as being profoundly contrary to common sense"

This particular apologetics organization even goes as far as saying: "A wider cast of the net may catch a new species in the process of becoming reproductively isolated from its known relatives." That suggests that common descent might be their only real objection. But by their own admission, from the perspective of any "new species" there will always be a degree of commonality -- so what are we arguing about? Is it merely a question of degree?

I have been prompted to open this topic for debate in order to explore the theme of so called micro-evolution and speciation after seeing much talk about it in other threads. To start the ball rolling I would like to know what practical limits there migth conceivably be to the scope of micro-evolution.

[QED]

I like the way that this topic can be discussed without resorting to too many technical details. If it can be kept that way I would hope to see more people with opposing views joining in to have their say.

The "short period of time" has been measured for a dozen or so of the mass extinctions, and turns out to be about 10 million years. At 65MYA, kaplowie! the dinosaurs are gone. By 55MYA, we've got the Age of Mammals. Relative to the preceding Mesozoic, that's short. But it's more than one or two generations of mammals.

Thanks for bringing in this ball-park figure of 10 million years for the length of time required to switch from one major era of life to the next. Nobody can get a proper feel for this sort of duration -- it defies all attempts at imagining a history lasting this long. But just because we can't imagine it doesn't mean it didn't happen.

So when the creationists/ID crowd claim that while "micro-evolution" occurs, "macro-evolution" cannot happen, they are not talking biological processes. They are trying to claim that somehow, a sub-population cannot become isolated and experiencing changes different than thos of the main population.

The creationist argument thus is one of population stratification, not of biology.

Of course the two go very much hand-in-hand. This issue can't properly be understood purely in terms of Biology or Demographics alone -- the two are interacting all the time.

This tread has bunch of good stuff in it. We should make it mandatory reading for creationists.

I have a feeling that there may be a lack of voluntary participants. However, seeing as this question of micro-evolution keeps cropping up in other debates, we will have ample opportunities to vector people here to keep those debates on-topic.

[Cathar1950]

10 million years may just be an average. Some could be a million years others 15 million years. Considering I can hardly remember yesterday some times and my kids are always reminding me of things I didn't know I remembered even 100,000 years ago is not anything any of us and comprehend in a way that fits our experiences. Our recorded collective history is at best maybe 4 to 7 thousand years. Maybe 50 to 70 thousand years for humans being any where out side of Africa. A million years is over 10 times the unknown history of humanity. Whales have had their brain size for 40 million years. Some think they are really smarter then us. I hardly see any reason to argue. We have only had ours, for what, under a million? Give or take a million. The Himalaya mountains got here after the dinosaurs, I think. It is hard to even comprehend but it is better then magic and harder to spot the illusions. hey that made me think of a reason we can't take humans out of the classification as animals. Just think how little we would know it we didn't have something to compare ourselves with.

[Jose]

Of course the two go very much hand-in-hand. This issue can't properly be understood purely in terms of Biology or Demographics alone -- the two are interacting all the time.

Do we still call it demographics if it involves plants or marsupials? Maybe we do...I don't know. Whatever we call it, the key is having populations get split into sub-populations for one reason or another, so that they can't "swap genes." The rest, as they say, is history.

10 million years may just be an average...

I should try to dig up the paper...I have an image in my mind (where else would it be--in my foot?) of several graphs of species diversity vs time, with all of them showing about 10 million years from extinction-event to recovery of diversity. I agree with you, though, that it feels like there should be a fair amount of variation. That may depend on how extensive the extinction was. They were probably looking at the big ones, like the Permian and Cretaceous. Less extensive "events" shouldn't take as long to recover from.