Funded Grants

Discovering the evolved human brain phenotype

Neuroscience in the 21st century still lacks a basic description of what makes the human brain distinctive as compared to other animals. Yet it is clear that human cognition is strikingly unique. Our technological sophistication, capacity for understanding unobservable mental states, and ability to create and manipulate symbols is unrivalled. Humans engage in behaviors that are exceptional, such as the production of personal ornamentation, language, art and music, and the performance of religious rituals. The distinctiveness of human cognition in the natural world is a puzzle. Humans share more than 99% nonsynonymous DNA sequence similarity with chimpanzees, yet there seems to be an incredible discontinuity in the function of the brain between ourselves and our closest living relatives, the great apes (including orang-utans, gorillas, bonobos, and chimpanzees). In this context, one of the most important challenges of modern neuroscience is to understand exactly how the unique features of human behavior are mapped onto evolutionary changes in neural structure and are specified at the genomic level. Remarkably, however, aside from the observation that humans have brains that are more than three times larger than expected for a primate of their body size, there are very few studies that explicitly examine how the human brain differs from that of great apes. Defining the human brain phenotype in a comparative context is important because it will reveal the underlying biological basis of our species' novel behavioral capacities and our unique susceptibility to neurodegenerative and psychiatric diseases, such as schizophrenia, autism, and Alzheimer's disease.

My research is driven by an interest in how brains differ among species, how this variation is correlated with behavior, how it is constrained by the rules of biological form, and how it is encoded in the genome. A complete understanding of human cognition must have very deep roots – tracing genes to phenotypes, following neurobiological changes across the lifespan, and describing evolutionary specializations in humans and our close relatives. My research program has three complementary components. (1) Detailed comparative anatomical studies of brain regions implicated in the most unique cognitive abilities of humans, such as "theory of mind" and language; (2) Examination of the costs and benefits of brain size expansion with respect to energetics, neuronal morphology, and cell type distributions; (3) Investigation of the interaction between cerebral architecture and species-specific patterns of life history in humans (e.g., rapid early brain growth, an extended childhood, and a long lifespan). Understanding human cognition requires viewing the human brain phenotype in the context of its evolutionary history.