Neo-Darwinism is an attempt to reconcile gradual evolution by means of natural selection ("survival of the fittest") as proposed by Robert Charles Darwin (1809-1882), with developments in the field of genetics.

Darwinism asserted that evolution is a gradual process in which minute changes in organisms accumulate over time and eventually result in the appearance of new species. This transmutation was the result of breeding that favored the replication of specific traits that aided a species' overall adaptability, or "fitness".

However, Darwin only speculated about the means by which traits were passed on from generation to generation. Like many of his naturalist contemporaries, Darwin thought that paternal characteristics were somehow transmitted through the blood. This reliance on what was termed "blood theory" led Darwin to further conclude that unexpressed traits and variants could be diluted...