The Basic Process of Evolution The basic theory of evolution is surprisingly simple. It has three essential parts:
Billions of years ago, according to the theory of evolution, chemicals randomly organized themselves into a self-replicating molecule. This spark of life was the seed of every living thing we see today (as well as those we no longer see, like dinosaurs). That simplest life form, through the processes of mutation and natural selection, has been shaped into every living species on the planet. In the book "The Dragons of Eden," Carl Sagan summarized the theory of evolution in this way:
Accidentally useful mutations provide the working material for biological evolution -- as, for example, a mutation for melanin in certain moths, which changes their color from white to black. Such moths commonly rest on English birch trees, where their white coloration provides protective camouflage. Under these conditions, the melanin mutation is not an advantage -- the dark moths are starkly visible and are eaten by birds; the mutation is selected against. But when the Industrial Revolution began to cover the birch bark with soot, the situation was reversed, and only moths with the melanin mutation survived. Then the mutation was selected for, and, in time, almost all of the moths are dark, passing this inheritable change on to future generations. There are still occasional reverse mutations eliminating the melanin adaptation, which would be useful for the moths were English industrial pollution to be controlled. Note that in all this interaction between mutation and natural selection, no moth is making a conscious effort to adapt to a changed environment. The process is random and statistical. Can such a simple theory explain all of life as we know it today? Let's start by understanding how life works and then look at some examples.
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