The emergence of genetic variants linked to brain and cognitive traits in human evolution

Human evolution involved major anatomical transformations, including a rapid increase in brain volume over the last 2 million years. Examination of fossil records provides insight into these physical changes but offers limited information on the evolution of brain function and cognition. A complementary approach integrates genome dating from the Human Genome Dating Project with genome-wide association studies to trace the emergence of genetic variants linked to human traits over 5 million years. We find that genetic variants underlying cortical morphology (∼300,000 years, P= 4 × 10⁻²⁸), fluid intelligence (∼500,000 years, P= 1.4 × 10⁻⁴), and psychiatric disorders (∼475,000 years, P= 5.9 × 10⁻³³) emerged relatively recently in hominin evolution. Among psychiatric phenotypes, variants associated with depression (∼24,000 years, P= 1.6 × 10⁻⁴) and alcoholism-related traits (∼40,000 years, P= 5.2 × 10⁻¹²) are the youngest. Genes with recent evolutionary modifications are involved in intelligence (P= 1.7 × 10⁻⁶) and cortical area (P= 3.5 × 10⁻⁴) and exhibit elevated expression in language-related areas (P= 7.1 × 10⁻⁴), a hallmark of human cognition. Our findings suggest that recently evolved genetic variants shaped the human brain, cognition, and psychiatric traits.