Concluding Remarks

In this chapter, I conclude that ecology has been shown to explain variation in the size of brain regions in multiple species, which is not the case for any of the other hypotheses. I go on to suggest the steps that need to be taken to collect the requisite data: collecting data on size of brain regions with identifiable function, choosing the appropriate cognitive test and collecting data from appropriate species, better quantification of ecological factors along with data collected from individuals that differ in age, sex, and geographical location, and demonstration that better cognition confers fitness benefits. Each of these is in both principle and practice feasible, if challenging to assemble for one hypothesis/taxonomic group. With these data, we may eventually be able to shed light on what has caused human brains to become relatively large.