Author Profile

Joe Flood, Ph.D.

Dr Joe Flood is a social scientist and policy analyst specialising in housing and urban studies. For the past seven years he has been conducting several one name studies which depend heavily on genetic genealogy. He has recently published a 700 page book on the COAD-COODE project. He is administrator of the CORNWALL, COAD, CODD and BLOOD Y-DNA projects at FTDNA, and he has published several articles and lectured on genetic genealogy.

Recent Posts

Using STRs for Intra-Family Y-DNA Comparisons: Segmenting Markers

Notional tree diagram of four descendants of common ancestor using a segmenting marker.

Counting Y-DNA STR differences is a poor discriminator for members of the same family. Unless a very large number of markers are used, matching cannot be used with a statistically significant degree of accuracy to establish whether someone is more closely related even to second cousins. However there are other methods that may be used to distinguish degrees of relatedness. We present a simple and useful test which involves finding a “segmenting marker” which can establish relative consanguinity with some accuracy, and we give a real-life example of its use to show from which of two 17th Century brothers a man of partly unknown origins descended.