Time frame of autosomal tests

[BakodiP]

I was wondering what's the possible time frame of an autosomal test. As it seems to me it's not like mtDNA or Y-DNA, going back thousands of years. What do you think? Couple of hundred, one thousand, or more?

 

[Orillion]

I would say a few hundred years at best, since the amount of autosomal data from one given ancestor gets divided by two with each passing generation.

For example, let's say you have 8 generations between you and a 17th century ancestor: this particular ancestor's DNA would only represent approximately 0.4% of your genome. I'm not sure whether such a low number even has any significance at all. In short, it's probably impossible to trace one single ancestor using autosomal DNA past 5 or 6 generations.

(DNA experts, feel free to correct me if i'm wrong )