To separate the influence of random drift from active adaptation, the researchers looked for genetic differences between urban and rural mice that were too extreme to be explained by drift alone. (insidescience.org)
Genetic flow is the term for the potential of genetic differences in a single species to be passed around within a species. (science.howstuffworks.com)
But in the mid 1990s, several evolutionary biologists began to assess kinship by analyzing degrees of genetic difference among species. (sciencemag.org)