Few ideas in intellectual history have been so captivating that they have overflowed the discipline from which they came and spilled over into everything else. The theory of evolution is unquestionably one of these. Evolution was an idea so powerful that it seemed obvious when Charles Darwin offered it. After all, there were prominent evolutionists a century before Darwin. Charles Darwin merely presented a model that made the theory plausible. It was a model, though, that infected everything, and one that appeared to answer every question worth asking, no matter what the subject. The model had the potential to lead "to some great generalization which would finish one's clamor to be educated," wrote Henry Adams in the best-known autobiography of the Progressive Era. "Natural selection seemed a dogma to be put in the place of the Athanasian Creed . . . ."
The discovery of self-consciousness in reasoning that marks the beginning of the modern era contributed greatly to our understanding of intellectual frameworks as evolutionary. Today every theory of jurisprudence worth contemplating incorporates a theory of change, but not every theory of jurisprudence qualifies as 'evolutionary.' Rather, evolutionary jurisprudence refers only to those jurisprudential theories that explicitly focus on legal change, or that make use of a particular model to explain how legal change occurs. For example, one might classify theories of jurisprudence as 'evolutionary' if they rely on the model of natural selection created by Charles Darwin. Nothing in particular dictates such an approach. In fact, to describe as 'evolutionary' those jurisprudential theories that relied on Darwin assumes the chronology backwards. The theory of evolution by natural selection was a theory about the development of ideas long before it was applied to the development of biological organisms.
At the turn of the twentieth century both the Gilded Age political right and the Progressive political left found their ideologies in evolutionary models and passed these models on to their intellectual descendants. Both models were Darwinian, and both accepted the doctrine of natural selection. The difference between the Social Darwinists and the Reform Darwinists rested ultimately on questions not of science, however, but of political values. Each of the influential evolutionary models in jurisprudence was closely tied to a particular political view about the role of the state in the allocation of scarce resources. Within such a fundamentally political paradigm, the question how the law itself evolves was little more than a detail.
Hovenkamp, Herbert J., "Evolutionary Models in Jurisprudence" (1985). Faculty Scholarship at Penn Law. 1927.