Legal evolution is a branch of legal theory which proposes that law and legal systems change and develop according to regular, natural laws. It is closely related to social evolution and was developed in the 18th century, peaking in popularity in the 19th century before entering a prolonged hiatus. Legal evolution saw a revival at the end of the 20th century and is continued in multiple contemporary theories. Theories of legal evolution use a variety of methodologies, including elements of sociological, historical, philosophical approaches.
Methodology and theory
The term 'legal evolution' covers a broad range of theories with different goals and approaches, but there are several features which are shared. Theories of legal evolution attempt to provide an explanation for the ways law changes with reference to wider factors outside the legal system. For example, the German historical school suggested law developed alongside the nation containing it, an idea carried on by Henry Maine in Britain in his theory of 'progressive evolution'. Likewise, legal memetics explains legal development according to the interplay between external information in society and its process of 'encoding' within legal rules. Another common thesis is that legal development is progressive, with legal systems tending towards greater complexity, completeness, or 'advancement'. John Millar proposed, for instance, that legal systems progressed from hunter gathering societies with minimal property to modern systems of international commerce.
Theories of legal evolution deploy a wide range of methodological tools. The German historical school was noteworthy for its use of a rigorous historical methodology, paying close attention to primary sources and manuscripts. Similarly, a common source of material is anthropological studies, such as surveys of Native Americans, which evolutionary theorists use to deduce the progression of rules from primitive societies to modern market ones. The evolutionary theorist might also rely upon universal laws of morals or general sociological hypotheses to explain a natural trend in legal development. A persistent theme is the frequent use of scientific metaphor. Maine in his work "Ancient Law" drew upon scientific theories of geology and possibly Darwinism, whereas John Henry Wigmore argued that legal evolution was more like the complex interplay between planets. Similarly, legal memetics draws widely from biology and, as a subset of memetics, relies upon analogies between genes, evolutionary pressure, and the cultural transmission of ideas. Other theories are rooted in sociobiology, attempting to generalise from supposed universal features of humankind, or even living creatures as a whole, to explain the development of legal rules, institutions, and ideas.
History
Early-modern theories
The idea of legal evolution first appears in the 18th century. Peter Stein argues that one of the main impetuses in its development was the inadequacy of theories of immemorial custom, popular heritage, sovereign will, and natural reason in explaining how legal systems change. Early examples include Pufendorf and Grotius who, despite their status as exemplars of natural law theorists, recognised that 'government and private property are not 'original' but appear only when man is ready for them'. They were followed by David Hume, who, as part of his argument against social contract theory, suggested law and government formed as a matter of habit over time. A French strand in evolutionary thinking developed simultaneously and was closely followed by the subsequent Scottish theorists. Montesquieu provided a highly detailed theory connecting law to society in 'The Spirit of the Laws', giving many specific examples of legal rules drawn from antiquity, contemporary law, and travel writers. However, he was unwilling to develop a general thesis of change, regarding it as unsubstantiated. Conversely, other French writers, such as Lafitau who compared Native Americans to the ancient Greeks, and Goguet, who traced economic and social effects on law, were willing to posit general theories of progress.