What you are seeing is a simply case of accident. High mutation rate STRs are prone to changing two or even three in one step. And having zero mutations in 200 years is very common. In my project we have people with one change in 800 years, just as expected as we have about 200 descendants from one person living then. Doug McDonald -----Original Message----- From: genealogy-dna-bounces@rootsweb.com [mailto:genealogy-dna-bounces@rootsweb.com] On Behalf Of Pete Beatty via Sent: Sunday, November 15, 2015 8:24 AM To: GENEALOGY-DNA Subject: [DNA] Genetic Collapse?? I am looking for more information on what has been suggested as a case of "Genetic Collapse" within my lineage. The Background: 1. Three individuals have been tested (STR @ 111, and SNP) 2. These three individuals have a common ancestor, proven through traditional research) that was married c 1795-1800. 3. Two individuals match of 67/67 and 111/111. The third has a 66/67 and 110/111. 4. The difference comes from DYS576 where the allele counts for the first two is 16 and the third is 19. 5. The mutation rate for DYS576 is 0.01109, or approximately 11 mutations every 1000 generations. 6. All SNPs are consistent.