Abstract
Evolution involves the repeated branching of lineages, some of which become extinct. The problem of determining the relationship between cortical areas within the brains of surviving branches (e.g., humans, macaques, owl monkeys) is difficult because of: (1) missing evolutionary intermediates, (2) different measurement techniques, (3) body size differences, and (4) duplication, fusion, and reorganization of brain areas. Routine invasive experiments are carried out in very few species (one loris, several New and Old World monkeys). The closest to humans are macaque monkeys. However, the last common ancestor of humans and macaques dates to more than 30 million years ago. Since then, New and Old World monkey brains have evolved independently from ape and human brains, resulting in complex mixes of shared and unique features. Evolutionary biologists are often interested in “shared derived” characters -- specializations from a basal condition that are peculiar to a species or grouping of species. These are important for classification (e.g., a brain feature unique to macaque-like monkeys). Evolutionary biologists also distinguish similarities due to inheritance (homology -- e.g., MT), from similarities due to parallel or convergent evolution (homoplasy -- e.g., layer 4A staining in humans and owl monkey. By contrast with taxonomists, neuroscientists are usually interested in trying to determine which features are conserved across species (whether by inheritance or parallel evolution), indicating that those features may have a basic functional and/or developmental role. The only way to obtain either of these kinds of information is to examine data from multiple species.
Meeting abstract presented at VSS 2012