I've actually taken a genealogical DNA test before, in June 2005, as part of National Geographic's The Genographic Project. They were studying isolated, indigenous populations but asked for as many participants as possible to send in their DNA to create a map of the human journey. I thought it sounded so interesting - how could I not be a part of it?
The results of the test put you into a haplogroup - depending on what mutations they find in your DNA, they can group you with others with that same mutation back to a common ancestor/group of people. The tree starts with a common ancestor in Africa, and from their branches out, and those branches branch out, and again, and it's on those various branches that your DNA will place you. The National Geographic website explains it much better than I do, so if you want to know more, I highly recommend visiting the site: www.nationalgeographic.com/genographic.
Anyway, I learned that I had four mutations that put me in haplogroup T. 40-60 percent of Western Europeans belong to haplogroup H, and as someone who seems to constantly strive to be different, I was happy to find I didn't fall into that group. T, though the second most popular Western European haplogroup, is only found in 20 percent of the population. Anyway, T is considered one of the main genetic signatures of the Neolithic expansion, which is basically when, around 10,000 years ago, hunter-gatherers became farmers. A lot of Ts can be found in the Ukraine/Russia/Georgia region, which I found interesting, because I was following an Irish line. Obviously, 10,000 years ago there were no Irish people. They all had to come from somewhere. But it was interesting to learn that where many of my branch ended up beside Ireland.