Natural selection has long been used as a weapon by evolutionists. They wield it like a sword in their war against Scripture, slicing their way through real science in an effort to promote their naturalistic agenda.
The theory of evolution by means of natural selection has long been based on the conclusions that come from several assumptions. The first assumption is that all species will produce more offspring than will be able to survive and reproduce more offspring and so on. Under the best conditions, a population will continue to reproduce at an exponential rate. The second assumption is that all organisms will vary in their ability to survive and reproduce. The third assumption is that some aspect of the ability to survive and reproduce are genetic and are passed on to the next generation. This last assumption is the most important of the three and the one that has been stressed the most. Even Charles Darwin emphasized this point in his historic treatise On The Origin of Species by Means of Natural Selection, or The Preservation of Favoured Races in the Struggle for Life.
These three assumptions then lead to the concept that one group of organisms (genotype) is more adapted to its environment and thus possesses greater fitness for surviving and reproducing. The conclusion is that certain genotypes with greater fitness will leave on the average, more offspring than do less fit genotypes. This conclusion is most often defined as natural selection.
Evolutionists go onto to say that because of natural selection, those genetic traits that promote a greater level of fitness will become more prevalent in the next generation. The increase in the frequency of these traits increases throughout the population and will eventually lead to gradual change in the entire population.
While the description of natural selection may sound simple, qualifying it is another story. Even many in the field of population genetics admit that there are numerous hurdles to overcome to be able to quantify the effects of natural selection.
One of those hurdles involves the ability to measure the biological complexity of fitness as described above. The only real way to test it would be to study the different isolated components of fitness. However, when these different components are separated or pooled together, they may alter the effects of a different component, making any test results questionable at best.
A second problem is the genetic complexity of fitness. The fitness aspect being examined may involve anywhere from one to many different genes. Identification of each and every gene along with its affect on other associated genes can require years of intense research. And this research can be easily contaminated by inadvertent environmental factors without the researcher realizing it.
Probably the largest hurdle to overcome in determining fitness is statistical. Selection of coefficients as small as 1% or ever smaller, can have a major impact on gene expression of any single gene, group of genes or all of the genes involved with the specific fitness trait being studied.
All this is to say that although you hear evolutionists using natural selection all the time, it is extremely difficult for them to accurately quantify their use of the term. Hence, it has become a catchall expression used to explain any change in a population or species of plant or animal.
While studying population genetics in graduate school, I realized that although natural selection may be near impossible to quantify, the effects of it are easily understood. Basically, natural selection is a population pressure that generally keeps the genetic variability of the population stable or it drives the population to a speciation event and eventually to extinction.
For example, the genetic variability within a large population will generally remain fairly stable. For the sake of the example, this large population has 1000 genes that are heterozygous (Aa, Bb, Cc, etc.) and 9000 genes that are homozygous, (XX, xx, YY, yy, ZZ, zz, etc). The only genetic variation exists in the 1000 heterozygous genes. The homozygous genes are fixed and are not variable. As the numerous individuals within that population continue to interbreed, the various genetic traits found in the 1000 heterozygous genes will be equally shared and dispersed throughout the population, thus preserving the overall genetic and physical make up of that population. However, if a small group of individuals from that population breaks away and moves to another location and no longer intermingles with the larger population, the amount of genetic variability can be reduced. Perhaps the individuals in the new population only have 950 heterozygous genes and 9050 homozygous genes. If this new population no longer interbreeds with the larger population, then only those genetic traits that they carried with them will be passed down to the offspring of the new population. Eventually, this new smaller population may or may not exhibit physical or behavioral differences from the parent population. If the differences are significant enough so that the two populations can no longer interbreed and produce viable offspring, it may be enough to declare the new population to be a separate species. But note that the formation of the new species is caused by the reduction in genetic variability not an increase.
With each new population that breaks off from the parent population, it continues to reduce the amount of genetic variability in the new populations. The more variability a population loses, the less likely they are to survive any changes to their environment. Eventually, a population may lose so much of their variability that their chances of surviving any type of environmental change are extremely poor, increasing the likelihood of their eventual extinction.
Or perhaps a major climate change occurs in the area of the parent population. Only those individuals that possess the traits necessary to survive the changes will survive. The forces of natural selection will select for those individuals best suited to survive in the new climate, while those that are less fit will die off. This can also reduce the amount of variability within the parent population. The same thing can happen with a disease or parasitic infection that affects a significant part of the population.
As stated before, natural selection either helps to keep a population stable, which means no change, or it will drive it to form a new species with a lesser amount of genetic variability and eventually to possible extinction.
When you think about it, natural selection could be considered an integral part of the Second Law of Thermodynamics, in which everything if left to itself will eventually break down and decay over time.
Now the question that has to be asked is: “How does natural selection support evolution which requires an ever increasing amount of genetic information or variability?” It doesn’t!
From a creationist point of view, God created everything to be very good. Undoubtedly, He would have placed a large amount of variation within the genetics of all or most of the plants and animals that He created. Then at the time of Flood, Noah (with God’s direction) would have most likely selected those animals with a greater amount of variation. We know this was so because of the tremendous number of different animals found in Post Flood deposits.
After the Flood and the animals dispersed off the Ark, the pressures of natural selection would have been very minimal, allowing rapid reproduction of most animals. As they rapidly reproduced, they would have started splitting off into different populations and moving into different regions of the world. The result would have been rapid loss of genetic variation resulting in rapid speciation. Eventually, the regions started to fill will animals and as it did, the pressures of natural selection would have increased in such a way to slow down reproduction and speciation. Many of the species created rapidly after the Flood became extinct because they most likely did not possess the genetic traits that allowed them to survive in their new climates and environments.
If evolutionists truly understood the effects of natural selection, they wouldn’t wield it like a mighty sword, for they will soon find that they will be the ones getting stabbed. However, creationists should wield the sword of natural selection because it truly does cut to the heart of the evolutionary model.