Humans are more alike than they are difference. For example, their brains are all the same color, if you will, regardless of skin or hair color. And humans all have blood—and it’s all red, again regardless of skin or hair color. However, actual blood types can differ based on ethnic diversity. Different ethnic and racial groups also have different frequency of the main blood types in their populations. An estimated 45 % of Caucasians are Type O, 51% of African Americans, and 57% of Hispanics are Type O. That means that type O is routinely in short supply and in high demand by hospitals, both because it is the most common blood type and because Type O-negative blood, in particular, is the universal type needed for emergency transfusions.