While I am not an expert by any means, I understand that the percentages of shared DNA in heritage / genetic lineage are the percentages of specific inheritable areas of DNA that only represent about 1% of the total DNA in the human genome. I think we all share about 99%. So yes, your 99.5% is probably correct, but in genealogical DNA terms, only the variable portion is considered.
I also agree - great article.

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