Organisation trumps size in primate brain evolution

The evolution of anthropoid primates, including monkeys, apes and humans, over the past 40 million years was largely driven by brain reorganization, and not brain size, according to new research from UCL. The study, which is published in Proceedings of the Royal Society B , found that around three quarters of differences between the brains of species of monkeys and apes are due to internal reorganization that is independent of size, dispelling the idea that variation in size is the primary factor characterising anthropoid primate brain evolution. Dr Jeroen Smaers (UCL Anthropology and UCL Genetics, Evolution & Environment), lead author of the study said: "The brain is central to how animals adapt and modify their behaviour in a changing environment.  "What we've found is that in relation to the brain, species differences are mainly explained by how the brain is organized and wired internally, not how large the brain is. This suggests that brain reorganization, not size, may have been the principal force driving brain evolution." To trace the evolutionary history of the anthropoid brain, the team collected the overall size of the brain and its internal structures for 17 anthropoid primate species. They then mapped and compared the evolutionary changes in these structures to get an insight into how the brains of each of the species specialised while adapting to their respective environments.