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Evolution for beginners (i)
Life, mutation and survival
By © Martin Foreman
Word Count: 796 words
Publication date: April 3, 2005
One of the more depressing items of news last year was the CBS poll which suggested that 55 percent of Americans believe that human beings were created in their present form by God.* Another 27 percent believe that evolution occurred under God’s guidance.
Only 13 percent – one in eight Americans – believe that the human race evolved with no input from God. Not surprisingly, the more education people have, the more they are likely to accept evolution.
Why do some people persist in believing that a supernatural being created the universe and the human race? Because creationism is simple and provides easy answers while evolution is complex and appears full of uncertainties. Creationism is for the mentally lazy, evolution for the mentally fit – and most Americans have flabby, underexercised brains.
So let’s get a mental workout with a primer on evolution. We can only scratch the surface of the topic, but we can still pick up the basic principles. This week we’ll look at the function of mutation. Next week we’ll look at complex organisms and try and fit God into the picture.
Starting at the beginning... The universe came into being between 11 and 20 billion years ago (we’ll discuss how this happened in a later column). Much more recently – about four and a half billion years ago - the earth formed from cosmic debris.
Rudimentary life began to appear about 500 million years later, when protein chemicals, perhaps stimulated by heat, lightning, other chemicals or radioactivity in the atmosphere, combined to form ribonucleic acid (RNA). This was not a miracle; scientists expect to be able to do the same in a laboratory within the next generation.
Without degrees in biology and chemistry it is difficult to fully understand the workings of RNA and its successor DNA or how they relate to human beings and other life-forms. But we don’t need degrees to understand the basic principles of evolution – reproduction, mutation and environment – which apply to all living things, no matter how simple or complex.
All life-forms reproduce. The simplest organisms divide to form identical offspring while the offspring of complex organisms combine traits from two parents.
Reproduction is not perfect. Every so often something interferes in the process. In single-celled organisms this may be different chemicals in the atmosphere or a slightly higher or lower temperature. The result is a “child” that is slightly different from its parent, perhaps with a molecule too few or too many or in the wrong place. A mutation has occurred.
Mutations are rare but inevitable. No-one knows how many reproductions have taken place in the last four billion years. Yet even if mutation occurs only once in a million reproductions, that still means that billions of mutations have occurred since life began.
A mutation can take any form. It may be so gross that the organism does not survive, or so minor that it is not noticed, like slightly longer ears. But in evolutionary terms, the only important mutations are those which affect the organism’s ability to survive.
A mutation that leads a bird to develop less efficient wings makes it less likely that the bird will survive and have descendants. A mutation which makes survival easier – such as a strong sense of smell to seek out food – enables the life-form to live longer and pass on the mutation to its descendants.
“Good” mutations enable life-forms to adapt their particular environment. The development of dorsal fins helped fish to swim, but would severely reduce a cheetah’s or ape’s mobility.
Every life-form is part of the environment for other life-forms, which means that a mutation in one affects many others. Antelopes have evolved to run fast enough so they can usually escape from lions, while lions have evolved to sometimes run fast enough to catch antelopes.
Mutations are not predictable and the circumstances in which they occur are not always clear. Why do peacocks have such gorgeous tails? Did the ancestors of giraffes always reach for higher leaves and a mutation occurred which made such feeding easier? Or did giraffes only start eating higher leaves when mutation led to longer necks? We may never know the answer to these and other questions, but they do not imply that evolution itself is incorrect.
To summarize: evolution rests on three basic principles: reproduction, mutation and environment. Life-forms reproduce. Mutations are inevitable. Evolution is the history of mutations that helped organisms survived in their environment.
Creationists argue that you can’t throw bits of metal into the air and expect them to fall to the ground as a watch. That’s true, but if you think that’s how evolution works, you don’t understand it. So next week we’ll see how mutation led life-forms to develop from simple organisms to something as complex as a human being.
* A poll by Gallup last year suggested that 45% of Americans were creationists.
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If God existed, he would...
admire the beauty of a universe that he did not create
recognize that eternity is meaningless
deny both heaven and hell
disown all men and women who speak in his name
denounce the harm caused by religious "morality"
help the human race to thrive without him
If God existed, he would be an atheist.
What is the difference between science and faith?
science is certain of nothing and requires proof of everything
faith is certain of everything and requires proof of nothing
Which do you trust?
"I know there is no God"
"I believe there is no God"
Check the answer
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