How whales took to water
Using evolution as their guide and knowing how natural selection works, biologists knew that the transition of early whales from land to water occurred in a series of predictable steps. The evolution of the blowhole, for example, might have happened in the following way.
Random mutations resulted in at least one whale having its nostrils placed farther back on its head. Those animals with this adaptation would have been better suited to a marine lifestyle, since they would not have had to completely surface to breathe. Such animals would have been more successful and had more offspring. In later generations, more mutations occurred, moving the nose farther back on the head.
Other body parts of early whales also changed. Front legs became flippers. Back legs disappeared. Their bodies became more streamlined and they developed tail flukes to better propel themselves through water.
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