Up to 1960s, mainstream evolutionists only believed that speciation requires “natural selection” and Japan’s geneticist Motoo Kimura launched a strong challenge to the idea. Kimura said that at the molecular level, most of the variation within a species does not come due to natural selection, but from neutral or close to neutral mutations caused by random genetic drift, which is neutral from the perspective of adaptation. This process is also known as a random genetic drift (Kimura, 1968).
The genetic drift theory is a non-Darwinian one. Initially, the theory met strong resistance from mainstreamers. In the 1980s, most of the evolutionary geneticists including Darwinian theorists accepted the theory as one of the mechanisms of evolution.
Kimura Motoo’s theory was directly related to advancements in molecular biology. In 1953, James Watson and Fredrick Crick discovered the double helix structure of DNA, which marked the beginning of molecular biology. In 1955, F. Sanger completed the amino acid sequence of insulin, which indicated a pathway of genetic information from DNA to proteins.
DNA is a long-chain polymer with its basic units called nucleotides. There are four different kinds of nucleotides, which are arranged into a DNA long chain that forms the genetic code. According to the DNA sequences, mRNA is synthesized. The mRNA is a template for the sequence of amino acids.
Each of three adjacent nucleotides in the mRNA works as a group, called a codon. During synthesis of a protein, the codon will determine the amino acid. Each site in mRNA may have four possible nucleotides. The three sites will have 64 (4x4x4) probabilities, which could code for 64 codons. However, only 20 amino acids correspond to the 64 codons. This means that some amino acids have two or more codons, such as the phenylalanine with its codons UUU and UUC.
Nucleotides in a DNA chain mutate at a rate of about one every 1 million or 1 billion. If a mutation occurs in DNA molecules, mRNA would change accordingly, alternation in mRNA codons might still code for the same amino acid, and the resulting protein would not change; this is the interpretation of genetic drift at the molecular level. There is no change in protein structure and function in genetic drift, therefore making no effect on survival. Neutral mutations can be preserved naturally, and frequency depends on opportunity.
Contradiction between the assumptions and inference
When one does not understand the reason for a particular phenomenon, assumptions are often necessary, based on which hypothetical reasoning is made. Assumption and inference must be consistent. If inference does not match reality. Initial assumptions should be modified or discarded.
Take SARS for an example. On November 16, 2002, there was the first outbreak of the disease in Shunde, Guangdong province, China. In the end of December 2002, Guangdong’s people turned up to talk about a deadly disease. Nobody knew the cause of the disease. There were different thoughts about the cause; it was thought that the disease was caused by a known bacteria or unknown bacteria, or a plasma, or a viral infection. Local doctors went to treat the sick patients with antibiotics and found them ineffective, and the culture results showed no bacterial growth; thus, they concluded that the disease is not caused by a bacterial infection. Here, the assumption is bacterial infection, the inference is utilization of antibiotics, the reality is antibiotics were useless. In this case, the assumption is consistent with the inference. This is the basic logic of thinking, and does not require a Ph.D.
Population genetics is an important branch of the biological evolution, on which the so-called “modern synthesis” is built, many mainstream evolutionists, including its founder T. Dobzhansky, are experts in population genetics. How do they explain the formation of a new species? They propose that mutations are accidental on individual that could extend to groups by either natural selection or genetic drift to a point it becomes fixed in the population, which is a new species. What is fixed? By definition, if by mutation of the entire group or 100% of the population would carry the mutation.
If a new mutation arises in an individual that could extend into a group, the individual must mate with others with healthy offspring, the individual and its mates have to belong to the same species.
The assumption is that individuals with the mutations can mate with other individuals and have children, the inference should be that they must belong to the same species.
However, the theory of genetic drift has incongruous assumption and inference. What the theory says is that initially, the mutated individual of the same species mates with other individuals. After awhile, they are not the same species anymore. If the theory were correct, the next question is how can it happen? Does the change happen one by one, or altogether. Who orders the change? All the mainstreamers can do is to ask you to apply a broad imagination.
This second question would be what organisms have genes that are 100% the same in the world? Like height, weight, and eye color, no individual in any group is exactly same. As far as a human with about 23,000 genes goes, there is no gene that is 100% the same or close to the same. Assume that mutation of a gene can be 100% by extending it to the entire group itself is against basic knowledge of molecular genetics.
Kimura, M. (1968). “Evolutionary rate at the molecular level.” Nature 217(5129): 624-626.