via unknowncountry by astrieber on 3/6/12
Evolution doesn't happen overnight: large changes in body size take a long time. There have been increases and decreases in mammal size following the extinction of the dinosaurs 65 million years ago. Now biologists estimate that a mouse-to-elephant size change would take at least 24 million generations, based on the maximum speed of evolution in the fossil record. PhysOrg.com quotes researcher Alistair Evans as saying, "A less dramatic change, such as rabbit-sized to elephant-sized, takes 10 million generations."Huge sea mammals, such as whales, took about half that number of generations to reach their current size.
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