Antigens

Scientists know that antigens make blood types different from one another. These body defences help protect our bodies from foreign invaders that might be harmful to us.

But that still doesn’t answer why blood comes in different types.

Different characteristics

These different blood types are suggested to each have special characteristics. Some fad diets even have specific meal plans that are tailored to match the different types.

Perhaps one reason for this is to keep the human population from being culled in one blow. Imagine if all of us had the very same blood type. We would all be susceptible to the same deadly diseases which could end up decimating our entire species.

Maybe having different blood types ensures that part of the population survives in the event of such scenario.