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I'm sorry, Carlos, but those samples don't come from the gens Julia.
They are the remains of normal people of the time buried NEAR the Mausoleum of Augustus. This is not like finding King Tut's tomb. We don't have the remains of any of the actual ruling families of Rome.
It's all in the Supplement of the original paper. This particular cemetery description is found on page 36.
"https://science.sciencemag.org/content/sci/suppl/2019/11/06/366.6466.708.DC1/aay6826_Antonio_SM.pdf"
My relationship to that cemetery:
26. Central Roman Mausoleo Augusto (500 AD) ..... 11.57 - R32 - (Click for more info)
Top99% match vs all users
My husband's:
3. Central Roman Mausoleo Augusto (500 AD) ..... 6.653 - R30 - (Click for more info)
Top99% match vs all users
Btw, Marcus Aurelius has nothing to do with the Gens Julia.
My husband is one of his greatest admirers. Still has his "Meditations" from university, and reads it.
It cannot be known.
It is an appointment of an author not related to the entire post, it is understood.
(It was in a different context. That time MyTrueAncestry was showing way larger IBD segments, but later the tool was updated.)1 cM by definition is the length of DNA that has a 1% chance of recombination during meiosis. For longer segments you can estimate the chance of recombination in a single generation based on the cM length. For example a 20cM segment has about an 80% chance of remaining intact and a 20% chance of being recombined. (It's not exactly 80/20 because it could have multiple recombinations). If the segment remains intact, there is a 50/50 chance it is passed down. For a 20cM segment of your parent's DNA, there is about a 40% chance you'll get the whole thing, 40% you'll get none of it and 20% it will recombine and you'll only get part of it.Obviously each generation decreases the likelihood of getting an intact segment of over 20cM from an ancestor. I could imagine a segment of that size surviving recombination for many generations, perhaps a few hundred years, but can't see how it would survive for thousands of year.
I wrote a recombination simulator. It is the first step in a project I may never finish to estimate the amount of DNA that should be shared by relatives based not only on the relationship, but by the number of males and females in the relationship path. (There is less recombination in males than females. You get 50% from each set of grandparents, but are likely to have fewer but longer paternal segments while you have more but shorter maternal segments).
I just ran my simulator a few times and the longest segment that it showed surviving 100 generations (roughly 3000 years) was about 7cM. I got quite a few segments 4-6cM and a few over 7cM, but none that were 8cM. I can't see how some of the images above are correct showing a segment over 20cM shared with someone who lived 3000 years, like shown in the first 2 images above (2450BC, 2500BC) That doesn't seem plausible to me.
Some of these shared segments are perhaps just IBS, non-IBD, with certain allowence of errors? Others could be real IBDs, but generally up to 3 cM for ancient blocks, I guess. Well, matching criteria may vary according to the tool. Still, these shared segments may point to certain particular genetic similarities, informative of (shared) ancestry. IBD sharing (recent/ancient blocks) is naturally used for tracking relations, even ancient, and anyone can Google it. There's a lot of stuff about.
That said, while I agree it's unlikely that large IBD segments survive for so many generations, it's not correct to assume segments will always be divided by two each generation. There's a limited number of crossover events which occur in each pair of human chromosomes - in somewhat random locations. The average is 2.5. Males tend to have less than females.
Figure 7 in the following paper shows an interesting representation of grandparents inheritance:
https://www.biorxiv.org/content/10.1101/194837v1.full
You may also inherit virtually an entire chromosome from a grandparent. This related article is interesting, and easy to understand:
https://dna-explained.com/2017/11/09/concepts-dna-recombination-and-crossovers
So, for example, if you inherited certain segment of DNA from a far ancestor, it's still possible you'll pass this same segment virtually intact to your child, and not necessarily half of it. Large segments naturally tend to be fragmented in few generations though.
I think this may help to understand some variations:
Or better:
https://gcbias.org/2013/11/11/how-does-your-number-of-genetic-ancestors-grow-back-over-time/amp/
(notice the same range in 10th and 11th generation: 0 to 1.5%).
The text below was posted by member mlukas in this thread, mentioning 23andMe user RandalGibbs. I'm a layman, but it seems to make sense based on what I read so far on the subject:
(It was in a different context. That time MyTrueAncestry was showing way larger IBD segments, but later the tool was updated.)
So 4-6 cM wouldn't be that absurd, according to the above.
@Duarte
Yes, pedigree collapse is also relevant. It's worth reading about it.
Sorry, Carlos. I know it's a disappointment, but it indeed can be known. The remains of a big group of people were found buried in the walls with almost no grave goods at all.
That's NOT how an emperor would be buried. His remains would have been in the Mausoleum, not inside the walls nears it, and he wouldn't have been put in a grave with "regular" Romans.
Not to say that his genetics wouldn't have been similar, of course. He had Plebeian as well as Patrician ancestors, as did many members of prominent Patrician gens of the time. Wealth was a great leveler, as was the case with the English aristocracy, for example.
It's just that there's no way we'll ever now how close he might have been to this particular genetic signature.
Wow is that yours?Silver Denarius - Empress Faustina Jr. AD 147 - 175/6
(Wife of Marcus Aurelius)
Roman Empress of Cordoba origin
Faustina the Minor. The young woman, whose family was a native of Espejo, married Emperor Marco Aurelio, who at her death consecrated her and founded a charity in her honor.
In fact he wrote me a very beautiful poetry for Christmas that said:
If you see an old woman and it's Good Night, tell her to come to your house.
It was recorded forever.
@Duarte
Yes, pedigree collapse is also relevant. It's worth reading about it.
She was born in Rome,
her great uncle, the emperor Hadrian, ...born in Italica, Hispania Baetica, into a Hispano-Italic family that settled in Spain from the Italian city of Atri in Picenum.
Mauseleo Augusto, many Villas, these people must have been loaded :grin:
Ancient relatives - Ancient Roman Samples - Only matches with "R"samples:
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