However, the main point is one even as we could have a great 17cM ancestral portion away from a good 4G grandparent, a great 5C is attending display element of by using us
-Gen 4: Ancestral locations (averaging 21 cM) out of your sixteen 3G grand-parents try spread-over regarding 159 areas. So you perform see, normally, an ancestral portion of per 3G grandparent within the roughly some other 10 places spread over the chromosomes in this genome. The brand new common avenues would mediocre 6.6cM, but a different way to look at this is the fact more or less 1 / 2 of of them is more than 7cM. not, feel means that a comparatively small fraction in our Matches is 4C and you may better household members. So might there be hardly any including Fits to cover most of the markets inside our genome.
-Gen 5: The thirty-two 4G grand-parents nonetheless provide us with rather large 17cM ancestral avenues (an average of) spread out more than 193 segments. We would nonetheless come across most of all of our 4G grand-parents in the numerous places. Our 5C Fits merely express, typically, 1.7cM. Thus not all of them, to the tails of your own shipping contours, tend to share 7cM or even more. Brand new counterbalance would be the fact we have a lot of 5Cs, that people still score a number of IBD fits with them. It can get numerous 5Cs, each which have good eight-10cM portion, partially overlapping our very own ancestral portion, in order to “cover” our very own 17cM ancestral phase. Used we quite often get 5C Matches which have over average places, but not often as huge as 17cM.
-Gen 6: The 64 5G grand-parents ticket off ancestral places to all of us one to average regarding the 15cM. It ticket these as a result of normally 227 segments; and each 5G grandparent tend to admission down DNA to 3 otherwise cuatro different locations, on average. Possibly some of all of our 5G grand-parents won’t have DNA you to definitely is located at united states whatsoever, while some my ticket down 5 or more areas – around, they usually averages away. At this level the majority of our Matches was 6C, promote or take a tiny. A great 6C, normally, just shares 0.4cM off DNA around. But you can find a lot of time tails within these shipments contours, And now we has actually loads of 6Cs. As a result, that we possess of many 6C who do express IBD places with us over 7cM. Yes, the possibilities of a certain 6C shared sector is just one forward the possibilities of a great 5C, but i have books 6C than simply 5C, we actually have more Fits which have 6C. This means way more 6C Fits try available with a provided part over 7cM, than you can find having 5C. Once more, it does normally capture some of them to “cover” and you can ancestral segment (a great TG).
-Gen 8: Missing a production to your 256 7G grandparents. Up until now you will find an average of 295 places, or around you to definitely part for each and every 7G grandparent. Demonstrably from this big date a number of the 7G grandparents don’t subscribe to your own DNA, and many 7G grand-parents donate to several ancestral avenues. Your own ancestral markets come in the latest eleven-12cM assortment, normally. And you may although 8Cs only show small amounts away from DNA normally, there’ll still be many 8C with common areas a lot more than a good 7cM threshold.
Although same analysis is valid playing with 23andMe and you may FTDNA data – both declaration of a lot Fits, both claim a little IBS speed (lower than 5%), by their prices, most of the Fits are beyond 4C
All through this analysis, the Overland Park escort service 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 per ancestral segment (TG)!