Genetic Variations and Evolution

Perry McCarney's image for:
"Genetic Variations and Evolution"
Image by: 

Genetic variation is the mainstay component of modern evolutionary theory. At its most basic level it is also fairly easy to understand, as it can be observed by anyone from any walk of life.

Look at the people around you, we are all human despite any jokes that might be made about some of our origins. And yet, except for the occasional identical siblings, we all vary in our appearance. This is a visual demonstration of genetic variation at work, although the genes are actually located in the same places within our genetic structure for the most part, what we have at these "loci" varies. The various possibilities are called "alleles". Some genes do not have very many if any variable possibilities or alleles while some have many.

Every human born has two eyes, there are no alleles to give us one or three eyes instead, but the color of our eyes can vary significantly because there are multiple alleles possible that produce proteins that will affect our eye color.

Now we come to the theory part, but before I start on that, perhaps an explanation of how the use of the word "theory" differs between its scientific usage and common usage. For most people a theory is a possible explanation for something. In scientific parlance, that is called a hypothesis. For a hypothesis to progress to the status of theory it must be testable and then it must be tested, usually through experimentation. It is not actually possible to prove a hypothesis through experimentation; all you can do is disprove it.

If after extensive and varied experimentation you have failed to disprove the hypothesis it becomes accepted as a theory. And that is far as it will go; in the past such theories were named laws, such as Newton's Laws, but that no longer occurs. So a scientific theory is as close as you are going to get a scientist to go in saying something is true, or leastways it's as far as they should go.

Genetic variation, as I hope I've managed to explain above, clearly occurs. Modern evolutionary theory holds that the genetic variation is acted upon over time by environmental conditions in a process called natural selection. In any population of a species, whether microbe, plant or animal, including humans, we have a natural variation of morphological (shape), physiological (function) and behavioral traits. The combination any one individual has will make that individual either better or less able in surviving their environment and more or less likely to successfully produce offspring.

Only those who successfully pass on some of their genes, or strictly speaking their alleles, will pass on their genetic traits to the next generation. In the Arctic circle white skin worked best as a camouflage from predators and blue eyes are better able to deal with the glare off ice and snow than brown. Humans with these genetic characteristics are therefore likely to have more numerous offspring than those without. In the tropics, those with high levels of melanin in their skin cells are better protected from the effects of the sun. Thus we have pale skinned blue-eyed people more common towards the arctic and darker-skinned brown-eyed people towards the equator.

It is the effect of this process of natural selection on those genetic variations through environmental factors, which includes such things as diseases, parasites and predators, that is the foundation of modern evolutionary theory.

The actuality of evolution is more clearly seen in organisms that have short lifespans. Scientists estimate that it takes approximately five million years for evolution, through the process called speciation, to produce new species in macroscopic lifeforms, those that we can most easily observe, ourselves and the animals and plants that we see daily around us or on nature programs.

Microscopic organisms generally have shorter lifespans. Evolution at work can most easily be observed in disease pathogens. The trillion-dollar pharmaceutical industry relies on this. There is a lot of concern being raised these days about the indiscriminate use of antibiotics to treat diseases caused by pathogenic (disease-causing) bacteria. This is because these short-lived bacteria are evolving; the environmental impact of antibiotics is eliminating those affected, resulting in the evolution of "super-bugs" who are immune. The original bacteria had a genetic range or variation, most were susceptible to the earlier varieties of antibiotics and died, the few that were immune lived to propagate.

This is evolution at work, one that is actually perceivable within our lifetimes. An area of consideration that those advocating creationist beliefs seem to ignore completely.

More about this author: Perry McCarney

From Around the Web