Saturday, November 14, 2009

Thoughts on Evolution and Genetics

I noticed something the other day. I was doing some research about some basic genetic theory (how genes are passed and expressed), and I see something that looks to be an issue for the evolutionary (macroevolutionary) paradigm. Please read last week's post "Is Evolution Repeatable?".

Let me start by describing the passing of genes via sexual reproduction. Every person has two genes that determine a specific feature- one from the mother and one from the father. The two genes (for instance) might be code for the color of eyes. One may be for blue, while the other is for brown. They both might be for blue and they both might be for brown. If a person receives two of the same, then that will determine the eye color. However, if one of each is received, the eye color is determined by which gene is "dominant" over the other. "Dominance" is a term that I don't want to get too far into, but suffice it to say that the dominant gene "hides" the existence of the other (recessive), so that it is the gene that the body uses. Just in case you're wondering, brown is dominant over blue, so is green. If you receive two copies of the same gene- dominance does not play a role- you will end up with that color (this is the only way that people can get blue eyes). Now, if you possess one of each, one of those will be transferred to your child(ren); however, it is not certain what determines which gene will be transferred- dominance plays no role in this.

It is widely recognized in the evolutionary community that an extreme minority (1 of 10,000) of mutations are useful to the organism. It is also recognized that generally bad or neutral mutations (the other 9,999) are not dominant (recessive). This means that bad mutations are not likely to be expressed in offspring (since the mate would not likely have a matching gene to compliment the recessive one passed). Which means that a bad mutation would not necessarily lead to the demise of an organism. Since its mate would not likely have a copy to pass to offspring, there is pretty much no chance that it would be expressed. The dominant/recessive property and behavior of genes establish a good "check and balance" or "quality control" to make sure that bad mutations are not expressed.

While nature is keeping the expression of these bad genes in check, it is working to eliminate them. Every gene has a 50/50 chance of being passed to the offspring, and the offspring has a 50/50 chance of passing further. This means that a bad mutation only has about a 3% chance of surviving beyond the fifth generation. The fact that sexual reproduction allows the removal of bad genes also seems like a "check and balance" system.

All systems that man is aware of that contains "checks and balances" or "quality control" have been designed. It is not a stretch to say that the same system at the genetic level may be designed also- it doesn't guarantee it, but by analogy, it makes it possible and even likely (since there is no "checks and balances" system that has been found that is known to be the result of random processes- one can't use nature in this case, because nature is the subject of the debate).

Now, I've only discussed the "bad" mutations. What about the "neutral" mutations? Since they are recessive also, they suffer the same survival probability that the "bad" mutations do. Lots of lines of argumentation that counter "irreducible complexity" and "chicken and egg" systems rely on the survival of many generations of neutral mutations. By the time that a sixth neutral mutation required for some "irreducibly complex" system comes along, the first is likely to be already eliminated and the organism's neutral mutations that are still there would have to wait for evolution to generate the eliminated gene again. While the surviving genes are waiting, at least one mutation will disappear with each generation, and they may also mutate to a point that they are unusable. Both of those compound the problem by forcing evolution to repeat itself.

The Long Term Evolution Experiment (LTEE) adds even more to the equation. One of the primary findings of the LTEE is that evolution has the ability to repeat itself only within one mutation (although it is rare). This means that the mate of an organism with a bad mutation may also have the same bad mutation. When the two mate, the offspring's chances of the gene being expressed rise from 0% to 25%. If it is expressed, natural selection will act upon it, which will eliminate the bad mutation more quickly.

What's really neat is that each generation may not see only a single mutation. Many mutations may take place with each generation. If even one of the bad mutations are expressed, then natural selection will eliminate them all by acting upon the one expressed. Unfortunately, if one good mutation gets caught with even one expressed bad mutation, it is kicked out also. Since only 1 of 10,000 mutations are good, they are not very likely, and a bad mutation can quickly cause the elimination of the already rare good mutation.

Back to the idea that the mate possibly has the same mutated gene...the more closely related the mates, the more likely they are to possess the same genes. If they both pass a bad gene to their offspring, that gene will be expressed.

If this process is correct, then Evolution cannot explain why sexually reproducing animals and humans exist today. According to the Evolutionary paradigm, sexually-reproductive animals began as a small population. In order to reproduce, inbreeding was required. In order for the population to survive the action of natural selection (eventual extinction) the genome must have been clear enough from bad mutations (to prevent their expressions) that its reproduction rate could "outrun" bad random mutation and the results of natural selection on those mutations. However, studies of animals going extinct have shown that reproduction can not "outrun" such a system. If that is true, then according to the Evolutionary paradigm, sexually-reproducing animals should have been made extinct shortly after their introduction into the natural realm. Due to the minuscule population the requirement to inbreed becomes necessary. That results in at least one bad mutation being expressed that causes natural selection to act upon the first offspring of sexual reproduction- stopping the propagation of sexual reproduction in the natural realm.

On the flip-side of the coin, this makes perfect sense from a Christian perspective. If the position that God created humans and animals with pristine genomes (no bad mutations to pass to offspring) in the first place is taken, then one can easily explain how reproduction could "outrun" natural selection (offspring would not accumulate enough bad mutations at each generation to be expressed and natural selection act upon them to make them extinct)- making for a large population. Since genes do not mutate in the same way at every generation, fewer copies of the same mutated gene are passed to offspring. "Inbreeding" is gradually phased out as a practice because of the larger population; however, if two people (closely related) with the same "bad" genes mate, then the offspring once again has a 50/50 chance of receiving two copies of the bad genes (which will be expressed) producing results ripe for natural selection to act upon (make extinct).

For more information on the expression of genes check out these links.
Mendelian Inheritance
Wikipedia's Article on Gene Expression

Other websites that I recommend for this discussion:
Reasons to Believe
Biochemist Dr. Stephen Meyer

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