Using Mice to Track Human Migration Patterns
Paul Harary ’19
Anyone who has ever found a mouse in their cupboard is acutely aware of the close relationship between humans and house mice. Indeed, the house mouse – mus musculus – is so named because it thrives in and around homes and other man-made structures. Scientists have long suspected that early agricultural settlements played a large role in the growth of populations of house mice. However, a recent study – led by Thomas Cucchi of the National Center for Scientific Research in Paris, France and co-authored by Lior Weissbrod of the University of Haifa in Israel and Fiona Marshall of Washington University in St. Louis – has shown that this commensal relationship may have begun as early as 15,000 years ago, with the sedentism of hunter-gatherers. By establishing themselves in one place for an extended period of time, hunter-gatherers served as a stable source of food and shelter for house mice, facilitating population growth of the species and the first stages of domestication.
The study attempted to uncover the reasons behind large fluctuations in the ratio of house mice to wild mice populations at ancient Natufian hunter-gatherer sites during different prehistoric periods. The Natufian culture existed in the Eastern Mediterranean and is one of the best examples of a semi-sedentary population before the advent of agriculture. By analyzing fossilized mice teeth found at the sites and comparing those linked to house mice with those linked to wild mice, the team was able to construct a timeline of the population variations. They then contrasted these numbers with known hunter-gatherer migration patterns and discovered a strong relationship between human mobility and the proliferation of house mice. It appears that the more infrequently the hunter-gatherers relocated, the more successful house mice were in outcompeting local wild mice. Prehistoric human migrations were often driven by weather patterns with periods of drought often associated with food shortages and relocation. Consequently, these arid conditions were often correlated with declines in the house mice population.
Many of the study’s findings were derived from the use of a new technique called geometric morphometrics, which uses Cartesian geometric coordinates to analyze differences in shape and structure. In this case, Cucchi harnessed this technique to distinguish between house mice and wild mice fossils, since the remains of the two species often appear virtually identical. As a result, he was able to correctly classify archaeological samples from Natufian excavation sites to an extremely high degree of accuracy.
The strong relationship between house mice populations and human migration patterns established by this study introduces the possibility of using the former as a tool to conversely understand the ecological impacts of early human mobility. By studying variations in the proportion of house mice to their country cousins, scientists can further unravel the complex interactions that took place between hunter-gatherers and the animals with which they co-existed.
References:
- Washington University in St. Louis. “Mouse in the house tells tale of human settlement”. ScienceDaily. ScienceDaily, 27 March 2017. Retrieved from: sciencedaily.com/releases/2017/03/170327172827.htm
- Weissbrod, L., Marshall, F. B., Valla F. R., Khalaily H., Bar-Oz G., Auffray J. C., Vigne J. D., & Cucchi, T. (2017). Origins of House Mice in Ecological Niches Created by Settled Hunter-Gatherers in the Levant 15,000 y Ago. Proceedings of the National Academy of Sciences. DOI: 1073/pnas.1619137114