[4] A main challenge in this research is the lack of empirical data: there are no archaeological traces of early human language.
[13][14] Although pre-Darwinian theorists had compared languages to living organisms as a metaphor, the comparison was first taken literally in 1863 by the historical linguist August Schleicher who was inspired by Charles Darwin's On the Origin of Species.
[19] August Schleicher and his friend Ernst Haeckel were keen gardeners and regarded the study of cultures as a type of botany, with different species competing for the same living space.
[20][16] Similar ideas became later advocated by politicians who wanted to appeal to working class voters, not least by the national socialists who subsequently included the concept of struggle for living space in their agenda.
[21] Highly influential until the end of World War II, social Darwinism was eventually banished from human sciences, leading to a strict separation of natural and sociocultural studies.
There had long been a dispute between the Darwinists and the French intellectuals with the topic of language evolution famously having been banned by the Paris Linguistic Society as early as in 1866.
The structuralists rose to academic political power in human and social sciences in the aftermath of the student revolts of Spring 1968, establishing Sorbonne as an international centrepoint of humanistic thinking.
It was eventually replaced by the approach of Noam Chomsky who published a modification of Louis Hjelmslev's formal structuralist theory, claiming that syntactic structures are innate.
An active figure in peace demonstrations in the 1950s and 1960s, Chomsky rose to academic political power following Spring 1968 at the MIT.
[22] Chomsky became an influential opponent of the French intellectuals during the following decades, and his supporters successfully confronted the post-structuralists in the Science Wars of the late 1990s.
[3] He argues that the Darwinian method is more advantageous than linguistic models based on physics, structuralist sociology, or hermeneutics.
[33] Also deriving from memetics and other cultural replicator theories,[3] these can study the natural or social selection and adaptation of linguistic units.
Inspired by 19th century advances in crystallography, Schleicher argued that different types of languages are like plants, animals and crystals.
Ferdinand de Saussure commented on 19th century evolutionary linguistics: "Language was considered a specific sphere, a fourth natural kingdom; this led to methods of reasoning which would have caused astonishment in other sciences.
Today one cannot read a dozen lines written at that time without being struck by absurdities of reasoning and by the terminology used to justify these absurdities”[56]Mark Aronoff, however, argues that historical linguistics had its golden age during the time of Schleicher and his supporters, enjoying a place among the hard sciences, and considers the return of Darwinian linguistics as a positive development.
Esa Itkonen nonetheless deems the revival of Darwinism as a hopeless enterprise: "There is ... an application of intelligence in linguistic change which is absent in biological evolution; and this suffices to make the two domains totally disanalogous ... [Grammaticalisation depends on] cognitive processes, ultimately serving the goal of problem solving, which intelligent entities like humans must perform all the time, but which biological entities like genes cannot perform.
Trying to eliminate this basic difference leads to confusion.”[57]Itkonen also points out that the principles of natural selection are not applicable because language innovation and acceptance have the same source which is the speech community.