Hi David, Thank you for sharing your experience. I have to correct one assumption in your post though. Not all people share the same pile ups. The person I talked about in my post is of Asian origin and she has pileups at different loci whereas she is missing the typical chromosome 2 Western Atlantic Autosomal Haplotype (WAAH) that most of us have. Andreas > On 13 Dec 2015, at 22:30, David Hamill via <genealogy-dna@rootsweb.com> wrote: > > I thought I would share my experience with a pile-up because it was instructive for me. > > I was building a triangulation group and started getting suspicious because too many people matched the segment. I apologize for forgetting the details here. By too many I mean something like 25% of the people on gedmatch when I did 1-1 comparisons with kits I suspected of being matches. I was looking at a relatively short segment (3-4cM?) so all these matches didn’t show up in the standard one-to-many search. I remembered the “pile-up” phenomenon and though I didn’t actually know what it was, it sounded like it might be an explanation of what was going on. I started checking kits totally at random and found a similar high frequency of matches. > > Researching Pile-ups I found that it refers to the phenominum where the percentage of people that have a particular segment is unreasonable based on any possible relatedness. The plausible explanation is that this genetic combination is favored by natural selection. > > Next I just looked for articles on pile-ups, and sure enough, the area where my too-frequent matches occurred was one that had been identified in several studies as one where these “pile-ups” are found. > > The point here is that pile-ups are not an aspect of ones particular group of matches but occur at the same places for everyone. I don’t know of a central compendium of pile-up areas that have been identified, but it would be nice if there was one. > > Maybe one quick and dirty way to see if a segment that appears to match for too many relatives is the result of a pile up, would be to see if it occurs in a similar frequency in both our relatives and kits selected at random…. Thats what tipped me off. > > In terms of the argument that it is caused by natural selection, what makes sense to me is that people for whom this area gets recombined due to crossovers are at a disadvantage (less likely to survive or reproduce) compared to people for home this region is intact. After all our DNA does have a job to do! > > David > > PS Of course just ignoring short segments in my case, I would have avoided the issue. I think what happened was I started with a few matches for a segment that included the pile-up area, and started looking for kits with related surnames who I thought might have a short piece of the same segment. And too many did….. > > >> On Dec 13, 2015, at 8:26 AM, genealogy-dna-request@rootsweb.com wrote: >> >> Message: 3 >> Date: Sun, 13 Dec 2015 10:56:24 -0000 >> From: Andreas West <ahnen@awest.de> >> Subject: [DNA] At what number of matches (at the same loci) are we >> talking about a pileup? >> To: genealogy-dna <genealogy-dna@rootsweb.com> >> Message-ID: >> <hJSp0t3pb-zqwGRIfEOeuWFWvSJGGA9D-CxJbhscXGdALUpl0@smtp.1und1.de> >> Content-Type: text/plain; charset=us-ascii; format=flowed >> >> Hi everyone, >> >> I hope we can find some consensus here and maybe some of you know even what >> number (of matches at a certain loci) is used by AncestryDNA to identify >> pileups. >> >> We're obviously not talking about 1000 here as that would give us 499500 >> 1-to-1 comparisons to run between the 1000 matches. That's the main reason why >> DTC DNA testing companies (and also GEDmatch) are interested to identify >> pileups to limit useless calculations (which in the end will still not find a >> single triangulated group (maybe) or it's too far back anyway, see the Timber >> algorithm used by AncestrDNA to cut matches. >> >> a) I have 97 matches (at the same loci) for one of my kits (at the "X" >> chromosome interestingly, it's a female person), which means 4656 >> combinations. Is that number already a pileup? >> >> How about: >> >> b) 52 matches = 1326 combinations >> >> c) 36 matches = 630 combinations >> >> d) 23 matches = 253 combinations >> >> e) 18 matches = 153 combinations >> >> Where is the line to draw? At a, b, c, d, e or where? >> >> >> What is the largest number of matches that you have in your triangulated >> groups? >> >> We obviously don't want to miss out a large TG as it also means a lot of >> people can "crowdsource" together and identify the CA much quicker than a >> group of 3 can (usually means also more family trees to compare with). >> >> Thanks for your answers! >> >> Andreas (WEST) born BASSO >> >> My ancestors: [http://www.wikitree.com/genealogy/Basso-Family- >> Tree-23](http://www.wikitree.com/genealogy/Basso-Family-Tree-23) > > > > ------------------------------- > To unsubscribe from the list, please send an email to GENEALOGY-DNA-request@rootsweb.com with the word 'unsubscribe' without the quotes in the subject and the body of the message

I discuss several kinds of pile-ups in a blogpost called Pileups. Some are good ones with segments over 9cM, and the pileup comes from many cousins from large families and/or distant Common Ancestors. They tend to cover TGs over 12cM. Some are smaller than 5cM and have been noted to occur in specific areas for many of us - there is an ISOGG/wiki that notes a dozen or so known areas. Some of us have noted some very "tight" areas, maybe 9cM wide with 100 or more 7-8cM segments that don't triangulate. These appear to be unique to individuals and occur at different areas for each person. These segments don't triangulate and are IBS. I don't think AncestryDNA has revealed which of these categories they find and delete pileup segments. My concern is that some pileups appear to be IBD and real TGs from a CA. The pileup term is being used in different situations. Jim - www.segmentology.org > On Dec 13, 2015, at 11:36 AM, Andreas West via <genealogy-dna@rootsweb.com> wrote: > > Hi David, > > > Thank you for sharing your experience. > > I have to correct one assumption in your post though. Not all people share the same pile ups. > > The person I talked about in my post is of Asian origin and she has pileups at different loci whereas she is missing the typical chromosome 2 Western Atlantic Autosomal Haplotype (WAAH) that most of us have. > > Andreas > >> On 13 Dec 2015, at 22:30, David Hamill via <genealogy-dna@rootsweb.com> wrote: >> >> I thought I would share my experience with a pile-up because it was instructive for me. >> >> I was building a triangulation group and started getting suspicious because too many people matched the segment. I apologize for forgetting the details here. By too many I mean something like 25% of the people on gedmatch when I did 1-1 comparisons with kits I suspected of being matches. I was looking at a relatively short segment (3-4cM?) so all these matches didn’t show up in the standard one-to-many search. I remembered the “pile-up” phenomenon and though I didn’t actually know what it was, it sounded like it might be an explanation of what was going on. I started checking kits totally at random and found a similar high frequency of matches. >> >> Researching Pile-ups I found that it refers to the phenominum where the percentage of people that have a particular segment is unreasonable based on any possible relatedness. The plausible explanation is that this genetic combination is favored by natural selection. >> >> Next I just looked for articles on pile-ups, and sure enough, the area where my too-frequent matches occurred was one that had been identified in several studies as one where these “pile-ups” are found. >> >> The point here is that pile-ups are not an aspect of ones particular group of matches but occur at the same places for everyone. I don’t know of a central compendium of pile-up areas that have been identified, but it would be nice if there was one. >> >> Maybe one quick and dirty way to see if a segment that appears to match for too many relatives is the result of a pile up, would be to see if it occurs in a similar frequency in both our relatives and kits selected at random…. Thats what tipped me off. >> >> In terms of the argument that it is caused by natural select

Are you saying that we actually know that Ancestry, 23andMe, FTDNA are going *back* into matches and deleting pile-up segments when they find them? So that our match lists can change retroactively? -----Original Message----- From: Jim Bartlett via <genealogy-dna@rootsweb.com> To: Andreas West <ahnen@awest.de>; genealogy-dna <genealogy-dna@rootsweb.com> Cc: David Hamill <dnhamill@aol.com> Sent: Sun, Dec 13, 2015 11:31 am Subject: Re: [DNA] Pile ups I discuss several kinds of pile-ups in a blogpost called Pileups. Some are good ones with segments over 9cM, and the pileup comes from many cousins from large families and/or distant Common Ancestors. They tend to cover TGs over 12cM. Some are smaller than 5cM and have been noted to occur in specific areas for many of us - there is an ISOGG/wiki that notes a dozen or so known areas. Some of us have noted some very "tight" areas, maybe 9cM wide with 100 or more 7-8cM segments that don't triangulate. These appear to be unique to individuals and occur at different areas for each person. These segments don't triangulate and are IBS. I don't think AncestryDNA has revealed which of these categories they find and delete pileup segments. My concern is that some pileups appear to be IBD and real TGs from a CA. The pileup term is being used in different situations. Jim - www.segmentology.org > On Dec 13, 2015, at 11:36 AM, Andreas West via <genealogy-dna@rootsweb.com> wrote:> > Hi David,> > > Thank you for sharing your experience.> > I have to correct one assumption in your post though. Not all people share the same pile ups.> > The person I talked about in my post is of Asian origin and she has pileups at different loci whereas she is missing the typical chromosome 2 Western Atlantic Autosomal Haplotype (WAAH) that most of us have.> > Andreas> >> On 13 Dec 2015, at 22:30, David Hamill via <genealogy-dna@rootsweb.com> wrote:>> >> I thought I would share my experience with a pile-up because it was instructive for me.>> >> I was building a triangulation group and started getting suspicious because too many people matched the segment. I apologize for forgetting the details here. By too many I mean something like 25% of the people on gedmatch when I did 1-1 comparisons with kits I suspected of being matches. I was looking at a relatively short segment (3-4cM?) so all these matches didn’t show up in the standard one-to-many search. I remembered the “pile-up” phenomenon and though I didn’t actually know what it was, it sounded like it might be an explanation of what was going on. I started checking kits totally at random and found a similar high frequency of matches.>> >> Researching Pile-ups I found that it refers to the phenominum where the percentage of people that have a particular segment is unreasonable based on any possible relatedness. The plausible explanation is that this genetic combination is favored by natural selection.>> >> Next I just looked for articles on pile-ups, and sure enough, the area where my too-frequent matches occurred was one that had been identified in several studies as one where these “pile-ups” are found. >> >> The point here is that pile-ups are not an aspect of ones particular group of matches but occur at the same places for everyone. I don’t know of a central compendium of pile-up areas that have been identified, but it would be nice if there was one.>> >> Maybe one quick and dirty way to see if a segment that appears to match for too many relatives is the result of a pile up, would be to see if it occurs in a similar frequency in both our relatives and kits selected at random…. Thats what tipped me off.>> >> In terms of the argument that it is caused by natural select -------------------------------To unsubscribe from the list, please send an email to GENEALOGY-DNA-request@rootsweb.com with the word 'unsubscribe' without the quotes in the subject and the body of the message