Glossary of "Ancestors in Our Genome" by Harris (2015)
- when gene versions that happen to be present at the frontier of a spatially expanding population, even if rare, ride the wave of advance and become quite common in the population after the expansion.
- Harris, E. E. 2015. Ancestors in Our Genome: the New Science of Human Evolution. - xx + 226 pp. Oxford University Press, New York.