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Evolution through natural selection happens much quicker than that. Sure, fish walking on land progression takes awhile, but otherwise it's pretty quick. htt

Evolution through natural selection happens much quicker than that. Sure, fish walking on land progression takes awhile, but otherwise it's pretty quick. https://www.sciencemag.org/news/2019/05/evolution-brings-extinct-island-bird-back-existence https://www.sciencemag.org/news/2019/05/evolution-brings-ext... As for the crabs, some of them still develop hard shells. They'll reproduce and the soft-shelled ones won't. So whatever it is that causes harder shells will persist.

btilly 7y ago
Evolution has a fast mode and a slow mode. The fast mode is that if there is enough genetic diversity in the population that a subset have a combination of traits that suffices, natural selection quickly will reduce the genetic diversity and all of the survivors will have those traits. The advantage of sexual reproduction is that much of the genetic diversity is retained and gets to recombine in interesting ways allowing the next challenge to be addressed. The slow mode is that if overcoming a barrier requires random mutations to produce new traits, it takes many generations for that to happen. The current pH allows some to survive and others not to. But with projected future pH levels, none will be able to survive. Therefore natural selection will select out the entire population as there isn't enough time for a new set of traits to evolve.