How does DNA research work - as applied to the distant history of populations, families, etc.?

Question

For example In Iceland recently, using DNA data, scientists discovered the geographic origins of the people, and the icelandic pony, and other important features of that country. How does this type of DNA resarch work and how is it done?

Answer 1

There are basic types of DNA for humans; people in one part of the world have mutations of one type; other people have another mutation. It is by tracing these mutations and sub-mutations that they decide where people came from, based upon samples sent in by various groups of people.
E.g., there is a haplogroup called R1b1, common in Western Europeans. R1b1 is futher subdivided, including R1b1c, which is further divided to include R1b1c4, R1b1c6, R1b1c7. Each of these are common to people that were the ancestors of people living in, say, Spain, Scotland, England, whathave you.
By studying what people living in a country now have in their DNA, they can trace migratory routes of people in the past.
Of course, it is not 100% accurate; but, it is more accurate than a paper trail, which is subject to rats, fires, all kinds of mistakes, and people deliberately changing the information.
By both paper trail AND DNA, I have traced my ancestors to all over Europe, including Iceland and including American Indians, Eskimos, and Innuits.
So, if you haven't yet, give www.familytreedna.com a try! It is fun!