In his famous work The Concept of Law Hart asked himself the question 'what is law?' Hart makes a very strict distinction between rules and morals: morals are rooted in biology, rules source back to society. Hart's sociological truisms have proven to be untrue, because modern evolutionary biology is not about the survival of the individual (or even of a species) but about the spreading of genes. This knowledge changes the fundamentals of Hart's theory and therefore his theory as a whole. In addition, my theory captures vital insights of Dworkin, legal realism, Posner and CLS, while at the same time forming a significant improvement upon them. In essence, the biological theory of law presented in this article is based on fractal patterns. Macroscale patterns recur in microscale patterns. The spreading of genes depends on important characteristics of genes: they are stable, they replicate, they need nutrients to replicate and they can cooperate. Superficially, genes, cells, organisms and groups may seem to act purposefully, but it is merely a pattern, with genes as generators, that brings structure to chaos. Human desires are in fact the needs of their genes. Thanks to language, morals can be put in words and become rules. To keep everyone working together, we need an ingenious device - like the law - to maintain that complex situations can continue to be judged on the basis of the simple principle of stability and reciprocity. To a degree, therefore, law itself can be derived from unconscious emotions and morals.