Sociocultural evolution justify new policies such as eugenics. Most 19th-century and some 20th-century approaches aimed to provide models for the evolution of humankind as a single entity. However, most 20th-century approaches, such as multilineal evolution, focused on changes specific to individual societies. Moreover, they rejected directional change (i.e. orthogenetic, teleological or progressive change). Most archaeologists work within the framework of multilineal evolution. Other contemporary approaches to social change include neoevolutionism, sociobiology, dual inheritance theory, modernisation theory and postindustrial theory. In his seminal 1976 book "The Selfish Gene", Richard Dawkins wrote that "there are some examples of cultural evolution in birds and monkeys,
Vestiges of the Natural History of Creation a very wide circulation. Darwin even suggested that Chambers' book helped pave the way for the publication of his theory of evolution by natural selection. "In my opinion it has done excellent service in this country in calling attention to the subject, in removing prejudice, and in thus preparing the ground for the reception of analogous views." The harsh reception that "Vestiges" received, and the mockery which was made of its evolutionary ideas, has been cited by some historians as a factor leading to Darwin's caution in publishing his own theory of evolution. In a letter to Thomas Henry Huxley