• Question: Why are there different blood types? How come everyone does not have the same?

    Asked by thelocalnerd26 on 7 May 2020.
    • Photo: Giulia Paci

      Giulia Paci answered on 7 May 2020:

      That’s a great question! Our blood type is determined by our genetic information (DNA) and the different types have evolved at different time. For example type A is the oldest while type B likely arises around 3.5 million years ago and so on. Why are they different? The different types came out of genetic mutations, and some of these mutations had an advantage (for example some blood types respond better to certain infectious diseases) so they were selected by evolution

    • Photo: Ailith Ewing

      Ailith Ewing answered on 7 May 2020:

      Hi! We inherit our blood group from our parents. What blood group we are is decided by just one gene, the ABO gene, and there are three different versions (or alleles) of the gene. One that relates to type A, one to type B and one to type O. But you inherit one version from your mum and one from your dad so what if you get two different versions? In this case if you get two the same then you will have that type, but if you get one A and an O then you will be A and similarly if you get a B and an O then you will be B. This is because the A and B alleles are dominant over O. Interestingly though A and B are what’s called co-dominant so if you get one of each then you will be type AB which is mixture of both A and B types. To be type O you need to inherit two O alleles (it is recessive).
      Great question and I’m sure lots of other scientists will add their thoughts too! ๐Ÿ™‚

    • Photo: Candice Ashmore-Harris

      Candice Ashmore-Harris answered on 7 May 2020:

      Your blood type is determined by the type of antigens stuck on the surface of your red blood cells. These antigens can either be made up of proteins or complexes of sugar molecules (polysaccharides) and which antigens you have depends on your genetic code (DNA). You can only make the antigens on your cells that you have the code for and you inherit this code from your parents. Because we don’t all inherit the same code people, even in the same family, have a range of different blood groups. Despite knowing about different blood types existing since the 1900s we still don’t really know if there’s a particular benefit or reason for having different kinds. It may be that certain blood groups are more susceptible to particular infections, but more study is needed for anyone to be very confident about this.

      If you’d like to read a bit further the NHS website can tell you how common different blood types are in the UK: https://www.nhs.uk/conditions/blood-groups/ and you can also read a bit more about the history of the different blood types here: https://www.smithsonianmag.com/science-nature/the-mystery-of-human-blood-types-86993838/ and here: https://www.bbc.com/future/article/20140715-why-do-we-have-blood-types

    • Photo: Kim Liu

      Kim Liu answered on 7 May 2020:

      This is a really cool question ๐Ÿ™‚ the others have written great answers which I can’t add further knowledge to.
      It’s interesting for me to think exactly how evolution would have given rise to this ~ as everyone has mentioned, it’s possibly related to how the different antigens react to different disease. But then, I wonder why we all don’t all have the AB blood type, which consists of A and B type antigens. On first glance this maybe would give the most ‘protection’? Probably protection is much more complicated that that – maybe A and B are bad if they coexist? Or maybe A is better for some function, and worse for others? It’s a nice example of how complicated life can be!


      After reading a little further – wikipedia says that there are 36 blood group systems consisting of 346 different antigens! Trying to understand why they all appeared … *brain explosion*

    • Photo: Nina Rzechorzek

      Nina Rzechorzek answered on 8 May 2020:

      Hello thelocalnerd26! Lots of great answers here; just to add – other species such as dogs and cats have different blood types too! You can read all about them here:

    • Photo: Roberta Migale

      Roberta Migale answered on 8 May 2020: last edited 8 May 2020 10:16 am

      GREAT question ๐Ÿ™‚ One of the most likely reason is different blood types can make someone more able to fight off disease. Some blood types are more prevalent in some countries than others and this may have made them more adaptable to diseases typically found within their region. For example, most people in Africa are group 0 which seems to be making them more resistant to malaria infection (the bug which causes malaria does not stick well to blood cells which are type 0!). This explanation is far from being entirely comprehensive and the reality still is we do not actually know entirely why different blood types evolved!