not, the primary point the following is that while we possess good 17cM ancestral section out of a great 4G grandparent, a great 5C is just planning to show section of that with all of us
-Gen cuatro: Ancestral markets (averaging 21 cM) from your sixteen 3G grand-parents is spread over from the 159 markets. So you perform come across, typically, an enthusiastic ancestral part off for each 3G grandparent in around various other 10 segments spread-over brand new chromosomes because genome. This new mutual locations carry out average six.6cM, however, another way to consider this to be is the fact more or less half of these would-be more 7cM. But not, experience implies that a fairly small percentage of one’s Fits are 4C and closer friends. So there are few instance Matches to cover every locations in our genome.
-Gen 5: Our very own thirty-two 4G grand-parents nonetheless give us fairly high 17cM ancestral avenues (an average of) spread out more than 193 locations. We could possibly nonetheless look for most of our 4G grandparents from inside the several segments. Our 5C Fits simply display, on average, 1.7cM. Very only some of them, towards tails of the shipments contours, often share 7cM or higher. The new offset is the fact we have too many 5Cs, we nonetheless score a lot of IBD suits together with them. It would grab multiple 5Cs, for each that have a great 7-10cM portion, partly overlapping our own ancestral part, so you’re able to “cover” our very own 17cM ancestral part. Used we often rating 5C Suits with more than average markets, but not often as huge as 17cM.
-Gen 6: Our 64 5G grandparents citation off ancestral places to all of us you to definitely average on the 15cM. They admission these down seriously to typically 227 markets; and each 5G grandparent have a tendency to citation off DNA to three or 4 different locations, on average. Possibly a number of the 5G grandparents won’t have DNA one to reaches all of us anyway, while others my personal admission down 5 or more areas – around, they usually averages out. At that top the majority of all of our Suits is 6C, render and take a small. A good 6C, on average, only offers 0.4cM from DNA around. But discover much time tails during these distribution contours, And now we possess a great amount of 6Cs. The result is we possess of a lot 6C who do share IBD markets around over 7cM. Yes, the likelihood of a particular 6C shared section is certainly one ahead the probability of a 5C, however, we have books 6C than simply 5C, we really attract more Fits which have 6C. It means a great deal more 6C Fits is available having a provided sector over 7cM, than just discover to own 5C. Once again, it will typically need the them to “cover” and ancestral phase (a good TG).
-Gen 8: Missing a manufacturing towards 256 7G grandparents. At this point you’ll find on average 295 areas, or just around one part for every 7G grandparent. Obviously through this date a few of the 7G grandparents don’t sign up for their DNA, and lots of 7G grandparents sign up to multiple ancestral markets. Their ancestral avenues are in the new 11-12cM assortment, normally. And although 8Cs simply share lower amounts out-of DNA normally, there will nevertheless be many 8C which have common places over an excellent 7cM threshold.
However the exact same analysis holds true having fun with 23andMe and FTDNA study – both statement of several Fits, both claim a tiny IBS rate (significantly less than 5%), and also by their estimates, the majority of the Matches is beyond 4C
All through this analysis, the number of ancestral segments has increased by a constant 34 with each generation; the average segment size starts off large and decreases with each generation, but even after 13 generation, the average ancestral segment is still over 7cM; the number of ancestors continues to double with each generation (and at some point duplicates will start to appear, but as I’ve outlined in Endogamy I and II, each duplicate really acts like a separate ancestor); and the average size of shared segments decreases by a factor of 4 with each generation, but we still see many Matches with shared segments over 7cM. To expand on this last point, I have over 10,400 “phased” Matches at AncestryDNA, with all the pile-ups and IBS already culled out. About 400 of these Matches are 4C or closer, leaving over 10,000 Matches in the 5C or more distant range. The distribution of these is spread out among 5C, 6C, 7C, 8C, etc. It is, so far, unclear how far back these go, but clearly there are many in the 5C-8C range. And AncestryDNA claims their “phasing” program has less than a 1% error rate. So 99% of these are IBD shared segments, probably most in the 6C-to-8C range. To my thinking, this means most of them must line up somewhere on our chromosomes. If we assume half, or 5,000, of these Matches are for each genome, on average, then these 5,000 Matches must be on 300 to 400 of my ancestral segments – or over 10 Matches in the 5C-8C range on every segment, on average. Some ancestral segments (TGs) may have more, some may have less, but the 5,000 IBD Matches have to go somewhere. I’ve picked on AncestryDNA here, because they poo-poo Triangulation (I think they don’t really understand it), and because they have equations that some have used to argue that we cannot have multiple 4C or above in TGs. All of these IBD Matches have to be on our chromosomes somewhere. And, in 14 months (by my estimation), we will have twice as many Matches as we have now – we’ll have over 20 Matches click now per ancestral segment (TG)!