Why human beings have diffrent blood group?
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Human blood types most likely came to exist to fend off infectious diseases. The incompatibility of some blood types, however, is just an accident of evolution.
There are four main blood types. Blood type A is the most ancient, and it existed before the human species evolved from its hominid ancestors. Type B is thought to have originated some 3.5 million years ago, from a genetic mutation that modified one of the sugars that sit on the surface of red blood cells. Starting about 2.5 million years ago, mutations occurred that rendered that sugar gene inactive, creating type O, which has neither the A or B version of the sugar. And then there is AB, which is covered with both A and B sugars.
There are four main blood types. Blood type A is the most ancient, and it existed before the human species evolved from its hominid ancestors. Type B is thought to have originated some 3.5 million years ago, from a genetic mutation that modified one of the sugars that sit on the surface of red blood cells. Starting about 2.5 million years ago, mutations occurred that rendered that sugar gene inactive, creating type O, which has neither the A or B version of the sugar. And then there is AB, which is covered with both A and B sugars.
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Rh called Rhesus factor is antigen that exists on the surface og the RBC .the blood groups which have this factor are demoted as -ve. there r 3 alleles A, B, I from which the blood group is determined
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