Natural science

As the sciences concerned with humanity split up into more specialized branches, many of the key figures of this evolution expressed influential understandings about human nature.

Darwin gave a widely accepted scientific argument for what Rousseau had already argued from a different direction, that humans and other animal species have no truly fixed nature, at least in the very long term. However he also gave modern biology a new way of understanding how human nature does exist in a normal human time-frame, and how it is caused.

Sigmund Freud, the founder of psychoanalysis, famously referred to the hidden pathological character of typical human behavior. He believed that the Marxists were right to focus on what he called "the decisive influence which the economic circumstances of men have upon their intellectual, ethical and artistic attitudes." But he thought that the Marxist view of the class struggle was too shallow, assigning to recent centuries conflicts that were, rather, primordial. Behind the class struggle, according to Freud, there stands the struggle between father and son, between established clan leader and rebellious challenger. Freud also popularized his notions of the id and the desires associated with each supposed aspect of personality.

E.O. Wilson's sociobiology and closely related theory of evolutionary psychology give scientific arguments against the "tabula rasa" hypotheses of Hobbes, Locke, and Rousseau. In his book, Consilience: The Unity of Knowledge (1998), Edward O. Wilson claimed that it was time for a cooperation of all the sciences to explore human nature. He defined human nature as a collection of epigenetic rules: the genetic patterns of mental development. Cultural phenomena, rituals, etc. are products, not part of human nature. Artworks, for example are not part of human nature, but our appreciation of art is. And this art appreciation, or our fear for snakes, or incest taboo (Westermarck effect) can be studied by the methods of reductionism. Until now these phenomena were only part of psychological, sociological and anthropological studies. Wilson proposes it can be part of interdisciplinary research.

An example of this fear is discussed in the book An Instinct for Dragons,where anthropologist David E. Jones suggests a hypothesis that humans, just like other primates, have inherited instinctive reactions to snakes, large cats and birds of prey. Folklore dragons have features that are combinations of these three, which would explain why dragons with similar features occur in stories from independent cultures on all continents. Other authors have suggested that especially under the influence of drugs or in children's dreams, this instinct may give raise to fantasies and nightmares about dragons, snakes, spiders, etc., which makes these symbols popular in drug culture and in fairy tales for children. The traditional mainstream explanation to the folklore dragons does however not rely on human instinct, but on the assumption that fossils of, for example, dinosaurs gave rise to similar fantasies all over the world.