Sociology
The Social Construction of Race and the One-Drop Rule
Quick fact
The one-drop rule, a US legal and social principle, held that any person with even one Black ancestor was Black. This rule had no biological basis; it was designed to preserve the institution of slavery and later, white supremacy.
Why this is interesting
You could be considered 'Black' even if you appeared white, simply because of a distant ancestor. How can a single drop of blood define who you are?