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Still no evidence for an ancient language expansion from Africa
On April 15, 2011, Science published a paper by Quentin Atkinson (University of Auckland, New Zealand), in which he proposed that the distribution of modern linguistic diversity shows traces of a single language origin in Africa. If this were true, it would increase the reach of historical linguistic inference by an order of magnitude. However MPI researcher Dan Dediu and his colleagues at Ludwig Maximilian University (Munich) cast doubt on Atkinson’s proposal, showing that with more realistic data and more appropriate methods the effect disappears. On February 10, 2012, their technical comments were published in Science.
February 10, 2012
In his paper 'Phonemic diversity supports a serial founder effect model of language expansion from Africa' Quentin Atkinson proposes that all modern human languages have an African origin. He suggests that the phonemic diversity of languages decreases the further away one goes from Africa, and that the underlying mechanism is a so-called 'serial founder effect' for language.
Apparently decreasing diversity
"In genetics, where the founder effect comes from, it means that when a daughter population splits off from a parent population, its genetic diversity is a subset of the parent's genetic diversity," explains Dan Dediu of MPI's Language and Genetics Department. "Thus, the daughter population will be genetically less diverse than the original parent population. If you repeat this process – this is called a serial founder effect – it results in further decreases of genetic diversity." Atkinson suggested an extension of this process to language, whereby daughter languages would repeatedly lose some of the phonemic complexity of their parent, leaving a trail of decreasing complexity the further away one moves from the origin of language expansion across the world.
Figure 1: Schematic map of possible language origins using different data and methods.
Atkinson reported an apparent negative correlation between the size of the phonemic inventory of a language and its geographic distance from West Africa. "Atkinson proposed that this is the result of a repeated linguistic founder effect accompanying the migration of modern humans out of Africa some 50-70,000 years ago," Michael Cysouw, Dan Dediu and Steven Moran note in their technical comments. "According to this proposal, the original languages spoken in West Africa would have had a large phoneme inventory, which became reduced during the spread of modern humans over the globe because of imperfect transmission in the small founder populations involved. From a linguistic perspective this result is surprising and contradicts our intuitions." They show that the decrease in phonemic complexity from West Africa is probably an artifact of the data, methods and assumptions used by Atkinson.
Top quality research
The authors of the comments however emphasize that their criticism strictly refers to some aspects of the paper under discussion, and not to other ground-breaking work by Atkinson. In fact, they “applaud Atkinson” for his proposal and for bringing new methods to bear on the old question of language origins and spread. "His research is top quality, there's no doubt whatsoever. But we raised some serious questions concerning the data and methods he has used in this study," says Dediu.
Link to the technical comments of Cysouw, Dediu and Moran in Science.
Link to Atkinson's response to the technical comments.
Link to Atkinson's paper in Science (332, 346).