In summary, by about 40,000 years ago, hominins had completed five important stages of cognitive evolution. As Homo habilis, about two million years ago, they began to become significantly more intelligent, and this trajectory toward becoming progressively smarter continued. As Homo erectus, about 1.8 million years ago, they developed self-awareness. As the Neandertal species of Archaic Homo sapiens, about 200,000 years ago, they acquired an awareness of what others were thinking, called a theory of mind.
