The Secret of Our Success: How Culture Is Driving Human Evolution, Domesticating Our Species, and Making Us Smarter

While natural selection traded strength for fat, increasingly complex tools and techniques drove another key genetic change: the human neocortex sends corticospinal connections deeper into the motor neurons, spinal cord, and brain stem than in other mammals. It is the depth of these connections—in part—that facilitates our fine dexterity for learne

As long as Homo erectus did not undergo further genetic alterations, its stone tools remained roughly the same – for close to 2 million years! In contrast, ever since the Cognitive Revolution, Sapiens have been able to change their behaviour quickly, transmitting new behaviours to future generations without any need of genetic or environmental chan

Like some insect societies, but unlike other great apes, Homo sapiens became eusocial, or highly social. At the same time, in-group sociality was matched by aggression toward out-groups. Cooperation within the group was forged by war between groups.

Exhibit C: Genes and cultures coevolve. Once our ancestors crossed the Rubicon and began to share intentions, our evolution became a two-stranded affair. People created new customs, norms, and institutions that altered the degree to which many groupish traits were adaptive. In particular, gene-culture coevolution gave us a set of tribal instincts: