Is Third Nature the Principal Internal Generative Driver of Human Gene–Culture Coevolution and Transgression? From Culture-Driven to Third-Nature-Driven Evolution: Brain Darwinian Machine–Culture Coevolution in Homo sapiens

Humans and other culture-bearing species participate in gene–culture coevolution: genes shape brains capable of learning and transmitting culture, while culture changes the selection acting on genes. A widely accepted view holds that culture is the principal driver: cultural innovation and social learning confer survival and reproductive advantages, thereby selecting for larger brains better able to learn. This paper accepts that account for birds, cetaceans, primates, other Homo species and early Homo sapiens, but argues that it cannot explain what happened in Homo sapiens after the emergence of Third Nature. In the 2020 book The Third Nature of Homo sapiens (Yuan & Yuan, 2020), NHP proposed that, with the emergence of an incipient Third Nature around 80,000 years ago, human gene–culture coevolution began to become brain Darwinian machine–culture coevolution, entering a phase principally driven by Third Nature that continues today. This paper reconstructs that claim in four steps. First, the production, selection and transmission of culture all pass through brains. Cultural feedback on genes can operate through diet, disease and ecology, but its source—culture itself—remains a product of brains. By overproducing neural connections during development and learning and selectively retaining some of them, the brain can be understood as a “Darwin machine,” to use Calvin’s term. NHP accordingly characterizes gene–culture coevolution in brain-bearing, culture-bearing species as brain Darwinian machine–culture coevolution, abbreviated below as brain–culture coevolution. Second, what determines what this machine selects is the brain's reward and value systems. In other species and early Homo sapiens, survival and reproduction supply the criterion, directing culture toward those ends. In Homo sapiens, Third Nature gives motivational value to represented, virtual and abstract objects and enables achieved goals to generate further goals. The selection criterion thereby extends beyond survival and reproduction. Human brain–culture coevolution is therefore Third-Nature–culture coevolution. Third, over tens of millions of years, no other culture-bearing species has transgressed. Limited accumulation is known in animals, but whether their cultures persist for hundreds of thousands or millions of years, they display no open-ended, directional accumulation beyond their existing functional domains and remain oriented toward survival and reproduction. Invoking that shared cultural-drive mechanism without identifying a specifically human difference cannot explain an exclusively human outcome. Threshold accounts based on population, connectivity and transmission fidelity explain whether culture can be retained and take off, but do not determine the direction of accumulation. Fourth, from Ecological-System Transgression through Genetic Transgression to the present, human transgression, the formation of the Cultural Cloud and most post-transgression phenomena exhibit effects of Third Nature: expansion beyond subsistence needs, goals directed toward virtual and abstract objects, the continuing generation of goals after achievement, and dissatisfaction amid abundance. These features exceed the survival-and-reproduction criterion underlying cultural-drive accounts. The conclusions are as follows. Gene–culture coevolution exists and is established. Cultural drive operates in other culture-bearing species, other Homo species and early Homo sapiens, whose cultures serve survival and reproduction; this holds on current reliable support. Cultural drive alone cannot explain the uniqueness of transgression or its direction beyond survival and reproduction; this holds on current reliable support. Since approximately 80,000 years ago, Third Nature has been the principal driver of human gene–culture coevolution: among the explanations compared here, it alone explains uniqueness, direction and open-ended expansion together. This holds on current reliable support, while its magnitude remains to be measured. The precise date and genetic basis of the transition remain pending determination.