As hominin brains grew in size and developed increasingly strong connections among various brain areas, we acquired intelligence, an ability to think about ourselves, an ability to think about what others were thinking (theory of mind), and then an introspective ability to think about ourselves thinking about ourselves. Finally, about 40,000 years ago, we acquired an autobiographical memory, an ability to project ourselves backward and forward in time in a way not previously possible. We had become modern Homo sapiens.
