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June 19, 2005
All Rights Reserved
World Copyright
© Martin Foreman
Column 11: Evolution for beginners (ii)
Complexity, sex and time
By © Martin Foreman
Word Count: 796 words
Publication date: April 17, 2005
Two weeks ago I wrote that, according to a CBS poll, 55 percent of Americans are creationists.* Here’s another sad thought: the same poll suggests that 65 percent of Americans want both creationism and evolution taught in schools. That makes as much sense as teaching about the tooth fairy in dentistry school.
In the previous column we saw that the basic principles of evolution are reproduction, mutation and environment. Life-forms reproduce. Mutations which increase an organism’s ability to survive in its environment are likely to be passed to its descendants. Given these principles, how did evolution lead from a single-celled organism to something as complex as a human being?
Billions of years ago, the only life on Earth was single-celled organisms which reproduced by dividing. Mutation meant that every so often a division failed. Most times, the organism would die, but at least once in our history mutation led to the creation of a new multi-celled life form, the second critical step towards complexity. (The first was the development of life itself.)
The new organism reproduced. With more cells, the opportunities for new mutations grew. Most had no impact, but at one point cells began to specialize in different skills such as mobility and digestion. The cumulative impact of different mutations in different environments then meant that over hundreds of millions of years, species as different as spiders, duck-billed platypuses and human beings emerged.
Put simply, the inevitable impact of mutation is complexity. Even something as complex as the eye is the natural result of evolution. There are many different kinds of eye, including the human version, which is actually one of the less efficient ways in which animals see.
Eyes began as light-sensitive membrane like skin, although skin now reacts differently. The most primitive eyes let the life-form detect shadow, which may mean a predator, and take evasive action. In time a transparent membrane, the original eyeball, developed, protecting light-sensitive cells from damage. Later, the eyeball would thicken to focus light and give a sharper view. In each case, life-forms with the new mutation would be more likely to survive than life-forms without them.
How did reproduction by single-cell division – one parent – become combination of genes – two parents? Sex is important in evolution because it significantly contributes to survival. The combination of two parents’ genes gives more opportunities for the resulting life-forms to adapt to and profit from their environment.
It seems that the mutation creating new combinations of genes in single-cell organisms occurred about three billion years ago. Perhaps another billion years passed before some bacteria moved from one cell to another, bringing their original host’s genes with them - in other words, the first sperm were bacteria.
This long, complex, often hit-and-miss process that we call evolution depends on one key factor: time. Human history stretches back only five thousand years and only in the last three hundred years has science developed to any great extent. Compared to the planet’s history, we have covered less than an inch in a one-mile race, an impossibly short period in which to observe evolution in action.
But if we cannot observe evolution directly, we can look at the evidence around us. From fossils to genes we are beginning to piece together the development of life-forms on this planet. The record is incomplete and not every detail is clearly understood. Nevertheless it is clear that evolution is the only explanation that fits all the available facts.
In our solar system, only Earth offers the environment that allows evolution to have come this far, although research may show that life progressed a little on Mars and some of the moons of Saturn and Jupiter before dying out. On those planets in other solar systems that have supportive environment, evolution has almost certainly led life on a very different path from here on Earth.
God is nowhere in this process because he is not needed. If you insist, you can have him set off the Big Bang. Perhaps every so often he stirs his creation up a bit – breathing life into RNA here, handing out tails there. But if that’s the case, when did he create humans? At what point did he say that this ape is still an ape, but its child is human?
Creationists can only discredit evolution by arguing that there is a chapter missing in the Bible, where God littered the earth with fossils to mess up our minds. “Yes,” says the Almighty, “the evidence points to evolution. But I cheated. And because you relied on intelligence not faith, I’m sentencing you to eternity in hell.”
Take your pick. Rely on the facts and deny God, or believe in God and deny the facts. Personally, I’m in favor of the facts.
* A poll by Gallup last year suggested that 45% of Americans were creationists.
Problems with the Biblical theory of creation... click here.
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