Why do people have different blood types?

Anyone who has donated blood knows one of the first things considered and tested is your blood type, to know how your blood might be used, and which patients have an acceptable blood type to receive your blood.  But a question that comes up from donors quite frequently is “Why do people have different blood types?”

User ZazzlekDazzle on Reddit explains the answer to this question to someone as if they were five years old:

Leave a Comment