A Segment-ology TIDBIT Up Front – it’s the one with the highest average cM among Match cousins. Setup: You’ve pretty much determined a particular couple are bio-Ancestors to youself (or someone else) – often by a consensus of Match Trees in a group (usually a Cluster) – see here. However, this bio-couple had a number of children. Which one of them was the bio-Ancestor? It gets harder and harder the more generations back you are researching. Process: I’ve had good outcomes by determining as many DNA Match cousins as possible for the bio-Ancestor couple. Line up the DNA Matches and the shared DN ..read more

Free eBook: Genetic Genealogy: The First 25 Years – 82 pages – the reflections of 34 Contributors – compiled and edited by Diahan Southard. This is a fascinating read from cover to cover. And it’s free to download here: https://diy.yourdnaguide.com/so-far I am honored and humbled to be included in this project. And a grateful hat-tip to Diahan who conceived this project; herded the cats to gather the various perspectives; curated and edited the inputs and got it ready before RootsTech 2024. And made it free to everyone! Thanks, Diahan Southard. [99C] Segment-ology: Celebrating the First 25 ye ..read more

A Segment-ology TIDBIT My previous post noted that ThruLines quickly adapted when I changed my Tree. Setup: I have looked at every one of my ThruLines Matches. If you are not sure, just open your DNA Matches list and select the Filters: Unviewed AND Common Ancestors. If you’ve looked at them all (and hopefully added appropriate information in the Notes box for each one), after a minute or two you’ll get a message: No matches match the selected filter. You’re now ready to take advantage of this status.   I have a pesky female Ancestor. I’m not really positive where she fits in a larger par ..read more

A Segment-ology TIDBIT I was entering a ThruLines line of descent into my Common Ancestor Spreadsheet, when I noted an error in the Match’s Tree. The Tree and ThruLines were at 6C. When I inserted the missing generation in my Tree, the relationship changed to 6C1R. As soon as I clicked back to the Match, the ThruLines was gone!  AncestryDNA now *knows* the correct relationship, and since it was beyond 7 generations for one of us, they won’t show it. Heads up. Copy or screen-shot before you lose the ThruLines link. I guess in a pinch, I could go back to my tree, take out the generation I a ..read more

As I look at ThruLines Matches under 15cM, roughly half of them have a Side (Maternal or Paternal) which is different from the Side of the Common Ancestor proposed. What’s up? AncestryDNA has determined a “side” (Maternal or Paternal) for most of my Matches. Pretty slick! And very helpful!! For above-20cM Matches they appear to be fairly accurate. This is despite the fact that all of my Paternal and half my Maternal Ancestor were mostly from Colonial Virginia. I was expecting a lot of Matches to be “Both”, but relatively few are. The bulk of my Matches are in the Maternal and Paternal categori ..read more

A Segmentology TIDBIT Ancestry’s ThruLines is like “dumpster diving”… sometimes you have to dig through the trash to find the pearls. Sometimes there is a smorgasbord of various genealogy junk, but sometimes there is a treasure trove of good information. Pick and choose wisely… [22CF] Segment-ology: ThruLines Levity TIDBIT by Jim Bartlett 20240211 ..read more

A Segment-ology TIDBIT Thinking about Small Segments and Distant Matches… Many have used the Speed and Balding IBD Statistics in Figure 2 of their Paper …  This chart has often been used to scare us away from small segments [by small I mean 7-to-15cM Shared DNA Segments – I do not encourage anyone to use smaller/”tiny” segments]. The vast majority of our Matches at AncestryDNA fall into this 7-to-15cM category, and I get many ThruLines Matches which have valid paper genealogies. They may not all link to the DNA, but I see no reason to discount them based on the small size of the Shared DN ..read more

A Segment-ology TIDBIT There are several key elements of good genetic genealogy – I’m going to call them Gold Stars. 1. DNA Match – as designated by the testing companies and GEDmatch. Most of these are our genetic cousins. I have a lot of them (over 120,000); and they are a good subset to work with. Worth a Star. 2. IBD Segment – We generally assume that virtually all Matches above 15cM have true genetic links; and my analysis is that about 66% of those 8 to 15cM are also true. Granted, some of the under-20cM Matches will be beyond a genealogy time frame (about 9 generations for me), IBD gets ..read more

A Segment-ology TIDBIT What if the genealogy is correct but the shared DNA is on the other side? Discard because the relationship is not from the Ancestor who passed down the DNA segment? Save because we are in fact real cousins, despite the DNA? Most of our real cousins beyond 3C won’t share enough DNA to be designated as a Match. Same quandary with a Match sharing one DNA segment, but related two ways. Both ways cannot be through the same segment. Now that Ancestry shows “sides” (Maternal/Paternal), I’m finding that some of the ThruLines are not on the same “side”. Sometimes this happenstanc ..read more

A Segment-ology TIDBIT A question recently came up: Are the Ancestors on two sides of a crossover point, always a mother and father (in either order)? Or: If I know the Common Ancestor (i.e. the father or the mother of the TG couple) of a TG segment, must the next TG segment be the other parent of the TG couple.? The answer is YES, with an important caveat: only when we are talking about mother and father of our Ancestor who created the crossover. Important scientific fact: A crossover is formed when a human recombines two Chromosomes to create a new Chromosome that is then passed to a child ..read more