Convergence

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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.[1] Coincidental matches can sometimes be in different subclades and the common ancestor will have lived several thousand years ago rather than within a genealogical timeframe. 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 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. 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, largely because the majority of people in the FTDNA database have not ordered any SNP testing. Robert Casey has estimated that perhaps only 5% to 10% of surname clusters are affected by the problems of convergence but for the people in such clusters perhaps 20% to 90% of their matches might be false positives.[3]

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Scientific papers

External links

Blog posts

See also

References

  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.