Corina Tarnita has a long-standing relationship with numbers. When she was deciding which research questions she wanted to pursue as a scientist, Tarnita realized that solving complex math problems was not it. “It was actually a really hard period because math was so intertwined with my identity,” she explained. Luckily, Tarnita soon found out that she could still feel the joys of mathematics while trying to understand a field that, according to her, was the complete opposite of math: biology.
After transitioning to the field of mathematical biology, Tarnita set course to explore how behaviors such as cooperation evolved within animal groups, even proposing new explanations for the emergence of eusociality—an elaborate social structure in which members of the same species cooperate to care for their young, exhibit division of labor, and often have overlapping generations.1 In 2011, The Scientist featured this and other early work by Tarnita in a profile.
The mathematical biologist’s approach to understanding different biological systems—from social insects to vegetation to humans—through a mathematical lens recaptured our attention 15 years later. As part of The Scientist’s 40th anniversary celebration, we talked to Tarnita once again about her work, which now explores the emergence of sociality in animals and the origins of regular spatial patterns in nature.
Finding Regularity in Natural Systems
In 2013, Tarnita started her lab at Princeton University, trying to figure out what directions she wanted to pursue as a researcher. After she and her colleagues published their new take on how eusociality could have evolved, an explanation that fueled heated debates in the evolutionary biology community at the time, Tarnita knew she wanted to step back from that research for a little while. “I wanted to actually do some new work,” she said.
Tarnita found inspiration when she traveled with her collaborator, ecologist Robert Pringle, to Kenya. As she shadowed Pringle and his team, Tarnita was struck by the uncanny regularity with which social insect nests and vegetation presented themselves in the African savannah.
The existence of regular patterns in nature, such as the North American Mima mounds or the Namibian fairy circles, is not new to scientists. Yet, understanding the processes that drive pattern formation has proven challenging, as many of these ordered patterns may take decades or more to form and cover thousands of miles, making experimental manipulation unfeasible.
To understand the triggers of spatial patterning in nature, Tarnita and her colleagues focused on termites and their nests. Some termite species build large, sophisticated mounds that stand out against the African savannah landscape. Using mathematical models and computer simulations, the researchers showed that territorial aggression between termites in different nests can lead to the generation of large-scale honeycomb-like patterns.2 “This hexagonal pattern, [in which] every termite mound has six neighbors around it, is a feature of a very competitive system,” Tarnita explained. “A system in which there's no more space, a system in which any small colony is killed instantly, and only the giants can persist, and they put these boundaries between each other.”
Tarnita’s team then expanded on these findings and showed that territorial competition interacts with spatial variability of resources to create the regularity seen in termite nests’ distribution.3 The team’s mathematical model suggested, for instance, that termite nests followed a highly regular pattern when resources were abundant and homogeneous across the area. Under these conditions, termite colonies are not pushed to expand their foraging boundaries, thus avoiding conflict with neighboring nests. These results provided evidence of how environmental factors interact with territorial aggression to influence the formation of patterns in social insect nests.
Going Back to Ants: The Emergence of Sociality
While Tarnita was exploring the mechanisms shaping large-scale regular pattern formation, her friend and collaborator Daniel Kronauer, a myrmecologist at Rockefeller University, was pondering one of the predictions Tarnita and her colleagues had made in the emergence of eusociality study. This was, “If eusociality was going to take off, it needed to come up with some important benefits in very small group sizes of very similar individuals,” Tarnita explained.1
To explore the origins of social organization in animals, Tarnita teamed up with Kronauer, who was studying the evolution of complex animal societies in a unique ant species: the clonal raider ant Ooceraea biroi. Tarnita explained that these ants were the ideal system to experimentally test the prediction she and her colleagues had previously made as these ants live in small groups in the wild and are genetically identical.
Combining laboratory experiments with mathematical modeling, the researchers confirmed the prediction by showing that social organization with division of labor arises in ant colonies when they reach a threshold of six individuals in the group.4 The emergence of this incipient form of division of labor, in turn, increases the group’s fitness as more specialized ant colonies manage the tasks they need to perform more efficiently.
For Tarnita, this work rekindled her interest in eusociality, a topic she is studying more broadly as her team explores the factors that shape social organization and trigger the emergence of sociality in its various forms.5
Understanding the origins of societies—with all of the within and between species variation, self-organization, and interaction with the environment—has remained the “holy grail” of Tarnita’s research. “[How to think about the origin of societies] has remained the question that keeps me up at night,” she said, “to find new ways to link what seem like different observations of nature and variation in nature into one story that kind of ties it all together.”
- Nowak MA, et al. The evolution of eusociality. Nature. 2010;466(7310):1057-1062.
- Tarnita CE, et al. A theoretical foundation for multi-scale regular vegetation patterns. Nature. 2017;541(7637):398-401.
- Castillo Vardaro JA, et al. Resource availability and heterogeneity shape the self-organisation of regular spatial patterning. Ecol Lett. 2021;24(9):1880-1891.
- Ulrich Y, et al. Fitness benefits and emergent division of labour at the onset of group living. Nature. 2018;560(7720):635-638.
- Staps M, Tarnita CE. When being flexible matters: Ecological underpinnings for the evolution of collective flexibility and task allocation. Proc Natl Acad Sci U S A. 2022;119(18):e2116066119.
