Traits that exist along a continuum, such as height, size, and behavior, vary significantly from person to person. The genetic and environmental interactions that cause these characteristics have long stumped scientists. In a recent study by Alvarado et al., ant larvae were exposed to an environmental factor that regulated adult ant size. The scientists were able to generate large and small ants just by changing the amount of exposure.

So how does ant size relate to the complex traits we see every day in humans? Though ant size appears to be modulated by a single mechanism, most complex human traits are determined by multiple factors that are not just environmental. For example, a combination of exposure to certain toxins in food or water, genetics inherited from your parents, and stress during development could all affect your susceptibility to develop diabetes later in life. However, the authors make a valid point about the importance of identifying small differences caused by the environment that could converge with other factors to vary traits. If tiny fluctuations controlled cancer cell growth, for example, then learning ways to manipulate them could be incredibly important.

Acknowledgements: Many thanks to Dan Tarjan, a graduate student in the Biological and Biomedical Sciences PhD program at Harvard University, and Holly Elmore, a graduate student in Organismic and Evolutionary Biology at Harvard University. Both provided expert commentary on the topic.

Managing Correspondent: Haley Manchester

Original article: Epigenetic variation in the Egfr gene generates quantitative variation in a complex trait in ants

Media coverage: Honey, I shrunk the ants: How environment controls size