Tuesday, October 20, 2009

Kinds, Taxonomy, Clades and Macroevolution.

>>"otherwise you're just witnessing the allowable variations and ADAPTATIONS within a specific "kind" of organism."

Your definition of microevolution, suffices to explain all life on this planet. You have arbitrarily defined macroevolution as something that evolution does not suggest will ever happen.

Evolution includes to a large part clades. Which is to say the common ancestor of a given organism and all of it's descendants. At no point will the common ancestor of two species in a specific group ever be something other than in that group. Humans and mice are both mammals and so our common ancestor will be a mammal. And though the ancestral mammals have given rise to sheep, whales, platypus, kangaroos, humans, lemurs, aye-ayes, elephant shrews, shrews, elephants, dogs, hyenas, bears and all the other mammals alive today. They will never become non-mammals. That's not the way evolution works. It is always about modification of previous forms. Not the change of one form into another.

Animals will never be non-animals. And mosquitoes and I share a common ancestor that was an animal. You are simply abusing a rather silly platonic idea and misunderstanding clades. The truth is "An X will never evolve into a non X" is true for all clades. It's actually a prediction and explanation of evolution. Any grouping that includes a group of closely related species must by definition include them all and they will never stop being that group. Even if the group is as narrow as the great apes which is only five main species (chimpanzee, bonobo, orangutan, human, and gorilla) or as wide as all of the animals. At no point will a human stop being an animal or stop being an ape.

The thing is the allowable variations within a specific kind are nearly infinite. So bats may always be bats, but if after a large extinction event they were a group to survive and have many millions of years of allowable variations they might troll the skies like birds of prey, graze the fields like cattle, some primates, and iguanadons of yesterage. Or fill the seas like penguins, whales, fish, or plesiosaurs. Even as these hypothetical bats burrow into other animals and live as parasites burrowed just under the skin they will still be bats. They would be bats if they returned to the seas, they would be bats if they burrowed in the ground, they would be bats no matter what kind of diversity they achieved. Oddly enough there are a lot of birds with this kind of diversity, some burrow, some in the oceans, some graze, some hunt at night with ears on their cheeks, some take to the skies with unrivaled vision and speed, and some scavenge for carrion or sing intricate songs. But, all birds are birds and they will never be anything different, just as all birds are the only surviving dinosaurs and will never be anything different, nor will they stop being tetrapods or animals.

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