From the point of view of biology and anthropology the human being is considered to be relatively undetermined, a ,flexible animal‘. The idea of evolution which became prominent in 19th century biology led to an awareness of the dynamics of legal development. Naturalistic assumptions about law began to dissolve. Recently, a new movement toward a biologically based natural law has arisen. But since the particularities of legal systems are not adressed, it is more accurate to speak of a biologically based naturalistic morality. Some authors, however, offer a biological explanation of the emergence of legal norms, in particular specify biological limitations on the effectiveness of law. The emphasis has been on biological limitations – genetic, brainphysiological, and behavioral – of human plasticity, on social control through legal norms. To the contrary it is argued here that we intentionally react to our biological constitution by creating legal norms. Nature does not determine the content of law.