1. ## 26% ancestry?

A TV commercial for DNA ancestry research has a women who says she found out she was 26% American Indian. It seems to me you are 100%, 50%, 25%,12 1/2% or some smaller percentage.
Ignoring the fact that I don't think you could be that high a percentage [unless adopted] without knowing it, how can you be 26% of any nationality? Can you help me with the math?

2. ## Re: 26% ancestry?

One explanation:

Suppose your mother's mother's parents were Native American and something else, but your mother's father's parents were both Native American. Then your mother would be 75% Native American. Now, suppose your father is 50% Native American. That makes you 67.5% Native American. Now, suppose you meet someone who is 25% Native American, your child will be 46.25% Native American.

Over the course of enough generations, you can wind up with just about any probability you want.

Another explanation:

DNA is able to tell heritage with a high degree of certainty, but not absolute certainty due to mutations (no child has a perfect combination of its parents' DNA. Every child has some mutations). Therefore, calculating heritage would give an expected value for heritage (an average) that does not directly correspond to a specific lineage. To put it another way, the scientists may be 95% confident that the woman has somewhere between 20% and 40% of her lineage as Native American, and the average (or expected value) is 26%.

3. ## Re: 26% ancestry?

Thanks. I should of used Native American to be PC. It was late and I could not drag it out of my tired mind. Thanks again