In the 1920s and 1930s, Gordon Childe revolutionized the study of cultural evolutionism. He conducted a comprehensive pre-history account that provided scholars with evidence for African and Asian cultural transmission into Europe. He combated scientific racism by finding the tools and artifacts of the indigenous people from Africa and Asia and showed how they influenced the technology of European culture. Evidence from his excavations countered the idea of Aryan supremacy and superiority. Adopting “Kosinna's basic concept of the archaeological culture and his identification of such cultures as the remains of prehistoric peoples” and combining it with the detailed chronologies of European prehistory developed by Gustaf Oscar Montelius, Childe argued that each society needed to be delineated individually on the basis of constituent artefacts which were indicative of their practical and social function. Childe explained cultural evolution by his theory of divergence with modifications of convergence. He postulated that different cultures form separate methods that meet different needs, but when two cultures were in contact they developed similar adaptations, solving similar problems. Rejecting Spencer's theory of parallel cultural evolution, Childe found that interactions between cultures contributed to the convergence of similar aspects most often attributed to one culture. Childe placed emphasis on human culture as a social construct rather than products of environmental or technological contexts. Childe coined the terms "Neolithic Revolution", and "Urban Revolution" which are still used today in the branch of pre-historic anthropology.