 Two new patterns in particular have been recognized by these DNA-based methods. The first is the preponderance of “purifying selection”, wherein the conservative power of natural selection is seen as a barrier to diversity. It is this conservative aspect of natural selection acting at the molecular level that lends power to the investigation of the genetic architecture of model organisms vis à vis human genetics. The second pattern is the discovery of the existence of ancient polymorphisms, molecular genetic variation whose age may be greater than that of the species or taxon in which it occurs. Natural selection remains the privileged explanatory force in modern sequence studies. Indeed, the search for, characterization, and explanation of uniquely molecular patterns, such as codon bias (Behura &amp; Severson 2013) and selective sweeps, has, if anything, elevated the focal explanatory power of natural selection in evolutionary studies. That is, nonrandom or biased use of redundant codons in DNA sequences is seen as evidence that, although they have no effect on amino acid sequence, redundant codons are not all functionally equivalent in that some permit more efficient gene expression. This is taken as evidence that natural selection is all powerful, reaching down into the genome to affect even the smallest and least significant components of the hereditary material.