Convergence (also known as evolutionary convergence) is a term used in genetic genealogy to describe the process whereby two different haplotypes mutate over time to become identical or near identical resulting in an accidental or coincidental match. Coincidental matches, even at 37 markers, can sometimes be in different subclades and the common ancestor will have lived several thousand years ago rather than within a genealogical timeframe. A case has also been reported of two 67-marker haplotypes with a genetic distance of 6, which were found to be in different R1b subclades.
One might think of convergence as producing "false positive" matches. One would ordinarily interpret a match as indicating a common ancestor but if convergence - rather than inheritance - is operating, there may be no common ancestor. The match is positive but false.
Convergence can be a particular problem for people who have a common haplotype such as the Western Atlantic Modal Haplotype resulting in a large number of matches. In such situations it is recommended to test a minimum of 67 markers. SNP testing should also be ordered to help rule out coincidental matches.
Robert Casey has estimated that perhaps only 5% to 10% of surname clusters are affected by the problems of convergence but for those people in such clusters perhaps 20% to 90% of their matches might be false positives.
- Larmuseau MHD, Vanderheyden N. Van Geystelen et al. Recent radiation within Y-chromosomal haplogroup R-M269 resulted in high Y-STR haplotype resemblance. Annals of Human Genetics 2014; 78 (2): 92-103.
- Chuan-Chao Wang, Ling-Xiang Wang, Rukesh Shrestha, Shaoqing Wen, Manfei Zhang, Xinzhu Tong, Li Jin, Hui Li. Convergence of Y chromosome STR haplotypes from different SNP haplogroups compromises accuracy of haplogroup prediction. Paper submitted to pre-print Arxiv server on 21 October 2013.
- Common haplotypes by Georgia Kinney Bopp
- Example of Y-STR convergence A diagram compiled by Mike Walsh showing a hypothetical example of convergence in R1b-P312 and R1b-U106.
- Smolenyak M and Turner A. Trace Your Roots with DNA. Rodale, 2004, p251.
- Mayka L. Coincidental convergence (or lack of divergence). Posting on the Rootsweb Genealogy DNA mailing list, 5 November 2012.
- Casey R. YSNPs - key to the future. YouTube presentation, 30 October 2013.