Dogs might be man’s best friend, but mice might be our most loyal followers. A new study shows that the history of house mice (in fancy Latin, Mus musculus) populations mirrors that of European human populations.
By using both modern-day samples, and ancient DNA from archaeological material, researchers were able to reconstruct their spreading during major human colonization events in the North Atlantic region, from Iron Age to modern times, based on mtDNA1. The results are nicely illustrated in the following figure:
During the Iron Age period and Roman times, the mice arrived from the Mediterranean region, accompanying the development of larger settlements and increasing human movement in the region. Next, during the Viking period, the many travels of these Northern people broadened the mice’s horizons across the north of Europe. The final colonization of new areas started with the rediscovery of America in the 15th century.
Two additional interesting points:
- Like in the human population, the genetic diversity of the Icelandic mice is quite low. This is probably the result of similar phenomena: the founder effect² and genetic drift³.
- Again, like the human population, the early Greenlandic mice population apparently failed to persist, and has been reintroduced later.
1mtDNA: mitochondrial DNA. In eukaryote cells, or cells containing complex structures enclosed by membranes, most DNA can be found in the nucleus (or ‘core’). However, there are other organelles (cellular structures) that carry their own DNA. Mitochondria, basically the energy-plants of the cell, are such structures. They carry their own DNA, and, interestingly, are normally only inherited solely from the mother.
²founder effect: when a small number of individuals starts a new population, this means that some genetic variation is lost.
³genetic drift: when the frequency of a certain gene version (or allele) changes due chance. Sometimes, surviving or not can be just a case of luck. (Notice that the founder effect is a special case of genetic drift).
Jones, E., Skirnisson, K., McGovern, T., Gilbert, M., Willerslev, E., & Searle, J. (2012). Fellow travellers: a concordance of colonization patterns between mice and men in the North Atlantic region BMC Evolutionary Biology, 12 (1) DOI: 10.1186/1471-2148-12-35