Big brains explained

摘要

Brain enlargement is one of the more conspicuous aspects of human evolutionary history. Although the benefits of a large brain seem obvious, the correlated survival and metabolic costs are immense and define much about the human condition. In Homo sapiens, giving birth to big-brained babies is risky. Furthermore, the energy consumed by the brain forms roughly 65% of a baby's total consumption and no less than 20-25% of an adult's, even though brain tissue accounts for only 2% of adult body mass.