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Convergence (also known as evolutionary convergence) is a term used in genetic genealogy to describe the process whereby two different genetic signatures (usually Y-STR-based haplotypes) have mutated over time to become identical or near identical resulting in an accidental or coincidental match.[1]

One can think of convergence as producing misleading matches – two men appear to be more closely related than they actually are. The same situation may result (very occasionally) if there is an exceptional lack of divergence. In other words, so few mutations occurred in the descendants of a common ancestor over the course of time that the common ancestor may appear to have lived only a few hundred years ago when in fact he lived much further back than that, perhaps several thousand years ago.

Parallel mutations and back mutations in individual STR marker values are the mechanisms by which convergence occurs.

Convergence is likely to be a particular problem within haplogroups R1b and I1 which both have a more recent origin but expanded very rapidly. The haplotypes which are most affected are likely to be those which are closest to the modal haplotype for the haplogroup, such as people who match the Western Atlantic Modal Haplotype or the so called Niall of the Nine Hostages haplotype. The presence of matches with a large number of different surnames is a possible indicator that convergence has occurred. Convergence is more likely to be a problem with low-resolution 12-marker and 25-marker matches, but does also occur with 37-marker matches. It is less likely to occur at 67 markers, though a case has been reported of two 67-marker haplotypes with a genetic distance of 6, which were found to be in different R1b subclades.[2] If convergence is a possibility then it is recommended to upgrade to a minimum of 67 markers and to order SNP testing to help rule out the coincidental matches which will have no genealogical relevance.

The incidence of convergence is not known, in part because the majority of people in the Family Tree DNA database have not ordered any SNP testing. Robert Casey has estimated that perhaps only 5% to 10% of genetic families or groups in surname DNA projects are affected by the problems of convergence but for the people in such groups perhaps 20% to 90% of their matches might be false positives.[3]

Scientific papers

External links

Blog posts and articles

See also


  1. Smolenyak M and Turner A. Trace Your Roots with DNA. Rodale, 2004, p251.
  2. Mayka L. Coincidental convergence (or lack of divergence). Posting on the Rootsweb Genealogy DNA mailing list, 5 November 2012.
  3. Casey R. YSNPs - key to the future. YouTube presentation, 30 October 2013.