The second phenomenon, random genetic drift, is the tendency of gene pools to lose neutral alleles over many generations. Each generation is but a random sample of the previous generation's variants, and as such is subject to sampling error just as a Gallup poll would be. Kimura's radical idea pitted neutral mutation against random genetic drift. Mutation pumps new neutral alleles into the gene pool, while random genetic drift purges alleles from it. This churning flux of alleles causes neutral mutations to accumulate.
Molecular evolution is a result of pure blind chance.
As a broad description of protein evolution this, the neutral theory of molecular evolution, has proved extraordinarily robust. After 30 years of intense research biologists have yet to provide a compelling picture of the molecular basis of a single ancient adaptive event. The difficulty arises from the very nature of the data collected. The linear sequences of amino acids in proteins, and of the nucleic acid bases in genes, are readily determined. By comparing the differences along these sequences it is possible to tease apart their historical relationships.