Lukas
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After all, who can say with certainty what is a bullshit and what is or who is right or wrong? One of the four major autosomal testing companies of the world says I have 1,165 cousins scattered around the world. Below, part of the list of some of the countries where I have cousins:
The first one on the list of cousins is a German woman, my first or second cousin, with whom I share 11 segments of DNA totaling 213 cm (3%), the longest being 51.1 cm. Neither I do believe in this, nor She, so much so that we never contact each other:
Just a genetic coincidence. Genes combine randomly. They play, they fun with us. She and me have only one genetic similarity. She is not my first cousin and neither am I her first cousin. I'm also not a cousin of the other 1,164 people that are on the list.
You don't understand it or just ********?
You compare matches of real people from MyHeritage with ancient samples from few thousands years?
Simply you can't inherit so many cM (50, 60, 80 or more) from ancient samples lived thousand years ago. This is clue of my post.
All those numbers are probably make up randomly for everyone who was sto stupid to pay for it.
Here is post from 23&me forum, not mine but user RandalGibbs.
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.