Which came first, overall bigger brains or larger brain regions that control specialized behaviors? Neuroscientists have debated this question for decades, but a new Cornell study settles the score. The study reports that though vertebrate brains differ in size, composition and abilities, evolution of overall brain size accounts for most of these differences, with larger brains leading to greater capabilities. The study is the first to compare – and resolve – two competing theories of brain evolution. One theory holds that natural selection drove progressive changes in particular areas of the brain, which then led to larger overall brains in species that needed them to survive. The other theory contends that some species acquired a bigger brain in general, and its larger basic parts could then be recruited for specific complex behaviors.