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Sideline
Guest
Since this seems to be the crux of the matter, I’ve skipped straight to it.Still, my original question was somewhat different. According to Mayr’s definition of stasis - “A period in the history of a taxon during which evolution seemed to have been at a standstill.” - I still haven’t seen a reasonable explanation for this phenomenon. I accept that a changing environment may drive evolution at a higher rate but, based on the “three basic facts” that Rossum listed in post #500, I don’t find any explanation for why evolution might virtually stop simply because the environment is stable, as those “facts” are independent of the nature of the environment.
Ender
Let’s do a bizarre and horrific experiment, shall we?
Let’s take 100 people and lock them into a big cage. Everyday they will play the same game over and over. The ten with the best scores get a feast, the ten with the worst scores don’t get fed at all. The rest get starvation rations, barely enough to survive. Like I said, it’s a bizarre and cruel experiment.
On the second day, who is most likely to change their strategy? Probably not the winners, right? The people who didn’t get fed are probably going to change the most.
Now let’s run this experiment over several months. You are going to find that some people died off who were just not good at the game. You will also notice that most of the people will use basically the same strategy. There will be variation still, but most people will follow along what works.
New ideas will constantly pop-up, but the number of useful innovations will decrease over time. Everyone will get better at the game, and the best strategies will become the most popular. Major changes in strategy will become uncommon, and what would be considered a radical departure will, to the outsider, be less radical. However, if there were ever a change in the rules (or in nature, the environment) then you would expect to see bigger changes.
Now in this scenario I haven’t accounted for the first one of rossum’s three points. I haven’t introduced offspring, but I’m sure you will agree that if we keep them in there long enough to have babies, they will teach their children the best strategies. This scenario definitely accounts for the lack of resources.
I know that the above example is artificial and fictional, but as a model, it really seems to show how stability in a population can occur.
I don’t know any way of slicing it: Stability favours stability. Change favours change. There are exceptions to the rule, but the rule works in most situations.