Brain evolution

Brains have evolved into a stunning diversity across the animal kingdom giving rise to an even more stunning diversity in behavior. What drives brain evolution? We have developed mathematical tools to help address this question.

Using these tools, we have found that cognitive ability and brain mass can be related by a simple equation. We have also found evidence suggesting that human brain expansion may have been driven by ecological rather than social factors.

Evolution of social behavior

During the evolutionary process, a group of individuals may evolve extremely high levels of cooperation and extremely low levels of conflict. This gives rise to a higher level individual, and such events have had dramatic effects on life on earth by producing for example eukaryotes from prokaryotes, multicellular organisms from unicellular ones, and "eusocial" organisms such as honeybees from solitary organisms. What causes such major transitions?

We have developed mathematical models to study a classic hypothesis that posits that one such major transition, i.e., eusociality, occurred because of manipulation. Specifically, the hypothesis suggests that workers in eusocial organisms evolved because mothers manipulated their offspring to become helpers. Although this hypothesis attracted interest in 1970's, it has received little attention partly because it has been thought that manipulation would lead offspring to resist, and so eusociality would be unstable in the long run. We have found that resistance may fail to evolve for various reasons, and that the patterns that emerge from manipulation are consistent with various patterns observed in eusocial taxa.

Species problem

Species are infamously difficult to define but they remain key units as evolutionary inferences and conservation policies rely on what is identified as a species. I developed a formalization of a classic notion of species, known as the biological species concept, and explored its consequences.

found that various difficulties of this classic species notion can be overcome by letting populations belong to multiple species.