My current research interests focus on the evolution of behavioural complexity and flexibility with the goal of understanding the adaptive benefits and evolutionary pathways driving evolutionary changes in cognitive architecture. The objective of the research is to understand what makes primate sociality distinct from other taxa and why and how humans have been able to develop large complex societies. There are several parallel themes to our research program.
The first is investigating evolutionary trends in brain size and architecture. Despite brain tissue being metabolically costly, relative brain size has increased over evolutionary time across mammalian taxa. Using a comparative approach, we test explicit adaptive hypotheses for the evolution of brain size and architecture. We have demonstrated that sociality is universally associated with large brains in mammals, but the relationship is strongest for primates (Shultz and Dunbar 2007; Perez-Barberia, Shultz, Dunbar 2007).This research has focused on a number of vertebrate taxa, including birds (Shultz and Dunbar 2010d; Shultz et al 2005) and primates (Shultz and Dunbar 2010b). We have provided the first quantitative test for encephalisation in mammals (Shultz and Dunbar 2010a). Most recently we have applied the approaches developed in other animals to understand hominin brain and cognitive evolution (Shultz et al, in press).
The second theme is to develop and use network theory to evaluate social complexity through measures of stability and structuring in animal populations (Stanley and Shultz, in press). We are currently developing this approach by assessing responses across ecological gradients. Equids are the current model system, due to the availability of data across wide ecological gradients, but the objective is to extend these analyses to evaluate variation and flexibility in primate network structure.
The third theme is to identify macroevolutionary trends in social behaviour using Bayesian statistics. Recent work involves reconstructing major evolutionary transitions in primate sociality and testing alternative models of social evolution (Shultz et al, 2011). We are now using this approach address questions about the evolution of mating systems in primates, and the distribution of marriage and kinship systems across human populations.
Finally, I am supervising projects that evaluate how species characteristics affect their sensitivity to environmental change (Salido-Grana et al, 2011).