To properly place the research needed to answer this question, we first have to appreciate the tremendous diversity of mammalian brains. For instance, brain size between mammals varies by a factor of approximately 100,000, with absolute brain size ranging from less than 0.1g in some bats and insectivores, up to 9,000g in sperm whales. Amongst the diversity, however, lies some kind of order. For example, all mammalian brains have a readily recognizable cerebral cortex, olfactory bulbs up front, a cerebellum in the back of the brain, and a brainstem that is contiguous with the spinal cord.
Using the comparative neuroanatomical approach on non-model organisms, we aim to determine commonalities of different brains, but we also want to find out in which way they differ. This will allow us to understand how evolutionary mechanisms give rise to this ordered diversity. Specifically, we are interested in the mechanism behind the evolution of large mammalian brains.