I just received the results of my mitochondrial DNA test, and am apparently of Scottish descent matrilineally as well.

Both men and women inherit mtDNA from our mothers. It's not used much in genetic genealogy, for two reasons. We are more interested in tracing surnames, which are inherited patrilineally, usually, so Y DNA, which men get from our fathers, is more useful in that project. Also, mtDNA mutates slowly, relative to YDNA, so those whose test results match yours are much more distantly related. In other words, it doesn't tell us so much.

Nonetheless, I tested and am in mt DNA Haplogroup H, as is close to 50% of the population of Europe, especially western Europe.

However, my low resolution matches are four in number. I share the same mtDNA with 2 out of 5,699 people whose ancestry is English, but with 2 out of 2,450 whose ancestry is Scots.

What I find remarkable is that it's been some 200 to 400 years since my ancestors came to the US, for the most part, and people of Scots descent are still marrying each other.