DNA Genealogy

[Dram]

Where does the data come from that says for example, you come from an ancient people in a specific area..

Through proven population samples. DNA has specific identifiable mutations that occur within a particular time frame. For example: our DNA is thousands of years old however, we can find common mutations in our DNA (I believe these mutations occur in populations where essentially the peoples become isolated to a particular geographical region) which become characteristics of a given population (Gaelic/Norse/Basque etc...) this process itself may take 1000 years or more. I'm sorry this is a vague answer...too much to consider writing here.

Is DNA collected from the remains of these ancient peoples found in archeological digs? How is the baseline determined?

DNA can be collected from remains. I am aware of some "bog-men" that scientists were able to recover DNA from. More commonly comparative DNA is gathered from proven samples of a living population. By proven, I mean someone who can trace their lineage back to a progenitor. For example: some Scottish clan chiefs have had their DNA tested because they can prove direct descendency from the originating line of the clan.

Wouldn't your ancestors have to have their DNA on record somehow? How could that possibly be obtained?

Your ancestors, ancestors are the historical record, and their descendents including you, me, and a ton of cousins depending on how far you wish to go back. It is the mutations on the markers of our DNA though that allow us to be "categorized" into cetain groups (families,clans, etc...) that narrows down our relationships considerably.