[SunkenCiv]

Great-great-great-great-grandparents, down to you. Most people have 23 chromosome pairs, which means that at least 18 of the gggg-gr generation didn't pass any of their genome to you, assuming there are no duplicates for that generations (because of criss-crossing lines of descent). The cell over the first 46 is just an illustration, not to show which ones were and were not, since there's (probably, usually) no way to know exactly. This doesn't mean some of your ancestors *weren't* your ancestors, they had to have lived (and had children) to make you possible, only that they didn't pass down any of their DNA to you. People related through that ancestor *may* have some of their DNA, perhaps all of it has survived in different family lines.

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46

18

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[SunkenCiv]

Thanks Little Bill for starting this topic, seems like a good one for GGG as well.

[Hawthorn]

>> People related through that ancestor *may* have some of their DNA, perhaps all of it has survived in different family lines <<

Exactly. Autosomal DNA testing will almost always show a match with one of your third cousins. But if you could test 100 of your proven fourth cousins, you probably would find matches with only 20 to 30 of them. And if you could test 100 of your proven fifth cousins, you'd be lucky to find matches with more than five or six.

On the other hand, Y-chromosome testing can give reliable results about your unbroken male-to-male line of ancestry going back thousands of years. And ditto for mitochondrial DNA testing, when it comes to your unbroken female-to-female line of ancestry.