Little genetic differentiation as assessed by uniparental markers in the presence of substantial language variation in peoples of the Cross River region of Nigeria
1 Centre for Society and Genetics, University of California, Los Angeles, Rolfe Hall, Los Angeles, CA 90095-722, USA
2 Novembre Laboratory, Department of Ecology and Evolutionary Biology, University of California, Los Angeles, 621 Charles E. Young Dr South, Los Angeles, CA 90095-1606, USA
3 Centre for Research on Language Contact, Glendon College, York University, Toronto, Ontario M4N 3N6, Canada
4 The Centre for Genetic Anthropology, University College London, Research Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK
5 Molecular and Culture Evolution Laboratory, Research Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK
6 Department of Anthropology, University of Kent, Canterbury CT2 7NR, UK
7 Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY 11794, USA
8 Department of Medical and Molecular Genetics, King's College London, Guy's Tower, Guy's Hospital, London SE1 9RT, UK
9 AHRC Centre for the Evolution of Cultural Diversity, Institute of Archaeology, University College London, London, WC1E 6BT, UK
10 Deptartment of Evolutionary Biology, Evolutionary Biology Centre, Uppsala, University, Norbyvagen 18D, SE-752 36 Uppsala, Sweden
BMC Evolutionary Biology 2010, 10:92 doi:10.1186/1471-2148-10-92Published: 31 March 2010
The Cross River region in Nigeria is an extremely diverse area linguistically with over 60 distinct languages still spoken today. It is also a region of great historical importance, being a) adjacent to the likely homeland from which Bantu-speaking people migrated across most of sub-Saharan Africa 3000-5000 years ago and b) the location of Calabar, one of the largest centres during the Atlantic slave trade. Over 1000 DNA samples from 24 clans representing speakers of the six most prominent languages in the region were collected and typed for Y-chromosome (SNPs and microsatellites) and mtDNA markers (Hypervariable Segment 1) in order to examine whether there has been substantial gene flow between groups speaking different languages in the region. In addition the Cross River region was analysed in the context of a larger geographical scale by comparison to bordering Igbo speaking groups as well as neighbouring Cameroon populations and more distant Ghanaian communities.
The Cross River region was shown to be extremely homogenous for both Y-chromosome and mtDNA markers with language spoken having no noticeable effect on the genetic structure of the region, consistent with estimates of inter-language gene flow of 10% per generation based on sociological data. However the groups in the region could clearly be differentiated from others in Cameroon and Ghana (and to a lesser extent Igbo populations). Significant correlations between genetic distance and both geographic and linguistic distance were observed at this larger scale.
Previous studies have found significant correlations between genetic variation and language in Africa over large geographic distances, often across language families. However the broad sampling strategies of these datasets have limited their utility for understanding the relationship within language families. This is the first study to show that at very fine geographic/linguistic scales language differences can be maintained in the presence of substantial gene flow over an extended period of time and demonstrates the value of dense sampling strategies and having DNA of known and detailed provenance, a practice that is generally rare when investigating sub-Saharan African demographic processes using genetic data.