Why Do We Have Different Blood Types?

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Why Do We Have Different Blood Types?

Human blood types mostِ likelyِ cameِ to exist toِ fend offِ infectious diseases.
The incompatibility ofِ some blood types, however, isِ just anِ accident ofِ evolution.
Type B isِ thought toِ haveِ originated someِ 3.5 million years ago, fromِ a genetic mutation thatِ modified oneِ ofِ the sugars thatِ sit onِ the surface ofِ red blood cells.