A new paper published in Cell on August 2 has refuted the widely accepted idea that uniquely human changes to FOXP2 led to the development of modern language, a notion often challenged but not fully dethroned until now. The new study shows that previous findings were actually false and that the evolution of modern language did not, in fact, hinge on changes in the FOXP2 gene, which is the currently accepted belief in textbooks.
The paper upon which our current understanding of language evolution is based, published in 2002, found evidence of a ‘selective sweep’ in which a mutation in the FOXP2 gene quickly spread across the population, an evolutionary process thought to have occurred over the past 200 000 years (2). The same team, led by Dr Wolfgang Enard, a geneticist of the Ludwig Maximilian University of Munich in Germany, have now repeated the study across a larger population and found no evidence of a selective sweep.
The original paper was based on the genomes of only 20 individuals but led to some important and widely accepted conclusions. The misconception was the result of selection bias, which simply means that the original population examined was not wholly representative of the entire human population ― the study examined individuals of European and Asian descent and only a few of African ancestry. The repeated study, however, was based on a more diverse population including both African and non-African individuals.
The FOXP2 gene was the first to be linked to language, discovered in the genome of a family with a long history of speech and language disorders. Despite the gene not being in involved in modern language evolution, FOXP2 is still thought to play a crucial role in language development. In humans, mutations in FOXP2 can affect the development of speech and language from early childhood, including apraxia, which makes it difficult to produce certain sounds, as well as problems with understanding, and issues with other language-related skills, such as reading, writing, spelling, and grammar. In mice, FOXP2 plays an important role in vocalizations and movement, which are also critical components of human speech.
The new finding sets an important example, suggesting that deciphering the genetic bases of evolutionary processes should be based on larger and more diverse datasets. Moreover, language — as well as other human functions — is complex, therefore its development and evolution are likely to involve more than one individual gene.
(1) Atkinson, E. et al. Cell (2018). DOI: 10.1016/j.cell.2018.06.048.
(2) Enard, W. et al. Nature (2002). DOI: 10.1038/nature01025