For the longest time, I thought to myself, "I'm actually quite racially pure. I can trace my ancestry to a specific province in Southeast Asia."
Then, I thought to myself, "Wait a minute. Then how come I sometimes get mistaken for all these other races? Heck, even though I'm well-traveled and (over)educated, why do I still sometimes mistake others for a race they aren't?"
The reason is simple.
Just like an individual is more or less the average of those closest to him/her, but not the same, so too it is with races and culture.
That's why when I see certain Poles here in Poland, I sometimes wonder how much German, Slavic, Scandinavian, Baltic, or Balkan blood they have in them. I also notice the similarities between these cultures, as well as the differences.
That's probably also why when certain people see me, they may wonder if I'm Indian or Pacific Islander. That's also why certain cultural aspects of my upbringing are similar to those of Indian or Pacific Islander descent, though there are some differences.
Now obviously, the further the distances become, the less similar the races and cultures get. But to think that race and culture is monolithic instead of a sliding scale doesn't make sense to me now.