Maybe the difference between Icelandic and Mapuche (a culture south of the Inca that were the last to fall to the Spanish). (provided Icelandic ancestors didn't somehow stumble into North America, marrying thier 800th cousins and messing up the whole family tree.

). Of course, it would happen with more isolated populations too.
Just food for thought (an intellectual exercise)... if a person had 4 descendants, and those had 4 each, and so on for each generation...
1st cousins - 16 (that's 4 siblings from the first set of parents, having 4 kids each)
2nd cousins - 64
3rd cousins - 256 (Guess how big my Polish side of the family is? It's at the 3rd cousin generation!

It's a little less actually, since the 2nd and 3rd generation have been having less kids. My great-grandmother would be the first generation, a little over 100 years ago. Our family is about to split, giving the 2nd generation is dying off, and now the 1st cousins have their own families. In 8 more generations, we won't even know of each other.)
4th cousins - 1,024
5th cousins - 4,096
6th cousins - 16,384
7th cousins - 65,536
8th cousins - 262,144
9th cousins - 1,048,576
10th cousins - 4,194,304
11th cousins - 16,777,216 (This is 250 years - If you use the 1940s as his generation, then that's 1690AD. Right around when the colonies started.)
Sounds like a typical day in Off Topic.