Natural Selection as a Mechanism for Evolution
A couple weeks ago, I started going over evolution and defining some terms in order to touch on various aspects of evolution and various theories about how that works. This week, I want to touch on natural selection as a mechanism for evolution (macro-evolution).
When people think of Charles Darwin, they think of “the theory of evolution.” As I pointed out already, however, Darwin did not develop the theory of evolution. What his theory was about was the concept of natural selection as a mechanism for evolution.
One famous example of natural selection had to do with moths. The basic gist of it (and I’m paraphrasing) is that light and dark colored moths would rest on light colored backgrounds. The dark colored moths were easily seen by birds and therefore were eaten. The light colored moths were difficult to see and did not get eaten by birds.
After a while, the light colored moths flourished and the darker ones all but vanished. As I recall, as a follow on to this, the moths in an area with darker places to stay ended in exactly the opposite result. Basically the idea behind it (and I know I probably completely messed up the actual details) that the moths that were difficult to see were safer and those that were easier to see were “naturally selected” for “extinction.”
So, the idea which is often understood as “survival of the fittest” is essentially the concept that nature will eliminate organisms that do not have attributes which are beneficial for survival. If an organism has a weakness that is easily exploited in or by it’s environment, chances are that organism will not survive and therefore not pass these traits to subsequent generations.
The biggest problem with this as a mechanism for evolution, however, is the fact that this results in something better referred to as “devolution” than evolution. Basically, the DNA code required for various traits ends up not being passed on to future generations whenever organisms with that code are “naturally selected” for termination.
An example might help to illustrate this.
Human beings are essentially all part of a single race. In fact, science has already determined that all human beings are descended from a single female and all men are descended from a single male.
Yet, we have people with various shades of skin. Black people, white people, medium brown people, “yellow” people, etc. We all have a certain amount of melanin in our skin which gives it its color. Those with higher amounts of melanin are darker skinned and those with less melanin have fairer skin.
To begin with, people had the DNA code for various shades of skin color. As people dispersed throughout the world, those with lighter colored skin survived better in colder climates and those in with darker skin did better in warmer climates. Over time, the DNA code required to provide a darker skin was no longer available in cooler climates and vice-versa.
As you can see, this natural selection process resulted in a loss of DNA information in a given lineage. This same cause & effect is evident in many of the variations of species. In fact, when one really takes a closer look at it, variation within a kind is actually what Darwin discovered and then extrapolated that out to the larger idea of evolution, though he did not actually find evidence to support that claim.
Darwin’s study was all done with respect to finches. Not only were these creatures all birds (kind), but they were even one particular family of bird…namely, finches. From there, the larger idea of evolution is an enormous leap to make. A leap which, finches with different sizes or shapes of bodies and beaks and such does not justify.
The fact is, natural selection does not add any information to the genetic code. In order for a species to evolve into something else over generations, new DNA code must be generated in order to build the structure of the organism.
Natural selection does not provide new data. That is why next week, I’ll take a look at one thing that actually can have the effect of creating new information for DNA and adding genetic codes for new features of organisms. That mechanism is referred to as “random mutation.”
Until then, grace, love and peace.