why is blood group o the most common group worldwide?

Answer 1

Boon Goonie is correct. Blood type O (-) is an universal donor, and can only receive blood type O. I never heard an explanation of why it is the most common group and as correrafan said, it is a recessive trait, and makes no statistical sense to be a majority. But the only think I can come up with is that both groups a and b were mutations. At some point the whole population was O and then one mutation to A occurred and it has been spread ever since. So even though it is not consider a mutation anymore, it's still a minority. The same could have occurred with B. If the mutation does not offer any advantage or disadvantage to the recipients survival as we believe, it will be passed on to the progeny unnoticed. If that is correct, the population of type O should be decreasing every generation, but we can only tell observing this rate across several generations. I have never seen any analysis of such figures so I have no idea if this is correct or not. But blood donation can become more complicated if type O becomes extinct...

Answer 2

I have always suspected that there is some unknown factor that makes this blood group more common. Group O is recessive to all other types, and usually the rule for recessive traits is that they are usually harmful in some way. Some more so, some less so, or negligible. Whenever a person with Group O breeds with a person of any other type, the offspring express the other type, not O. Since Group O is represented by about 38% of European Americans, this does not make any sense, unless there is another, unknown factor at work affecting the survival rates of other ABO Groups.

Answer 3

I didn't think that "O" type blood was the most common group. But if it is. Good. Type "O" blood can be donated to any other blood type. But a person with type "O" blood cannot receive from any other blood type. Other than "O". Am I correct on this readers?