What is the the evolutionary explanation for different blood groups?

Question: What is the the evolutionary explanation for different blood groups?

Asked by dumhead456 to Hermine, Katy, Laura, Nathalie, Paula on 22 Jun 2010 in Categories: General.
- Nathalie Pettorelli answered on 22 Jun 2010:
  
  Hi again,
  
  You have some pretty good questions – you are definitively making my morning! There is no concensus or very good answer to this question, as far as I know: what’s believed nowadays is that blood groups have appeared as mutations that got fixed in certain populations, with our ancestors being originally O type. What’s unclear is why these mutations got fixed – it could be random fixing (that is, a mutation appears, spreads and becomes the dominant morph within a population without bringing any advantage to the carrier), it could be that at the time the mutation appears it gave an advantage to the ones having it (i.e., selective advantage, making the mutation being retained more likely). Hope that helps 😉
- Katy Mee answered on 22 Jun 2010:
  
  Evolution is a change in inherited traits of successive generations and usually occurs in response to some triggering factor that dictates which traits are more important for survival than others (e.g. survival of the fittest). Since the difference in blood groups is to do with the variation in different antigens in the blood, it is likely that this evolution of blood was triggered by some of trigger on the immune system.
  
  So for example if a particular type of antigen proved to be successful at fighting off certain infections/diseases and that infection/disease was prevalent within that population, it is likely that those individuals with the ‘strong’ blood type would live lnger healthier lives and thus have healthier offspring. This natural selection is what causes traits to evolve.
- Paula Salgado answered on 22 Jun 2010:
  
  A very interesting question that has made me learn something new today! This is why I’m enjoying IAS so much! I’ll try and summarise what I learned:
  
  It was first thought that O was the original blood group and then mutations occurred that originated the A and B (and AB from combination of the 2). However, more recent studies indicate that this is not the case. Also, other higher primates like chimpanzees. gorillas and orangutans have similar blood group types.
  
  There are lots of ongoing studies trying to understand how the different groups evolved and are distributed. Also, they are trying to understand if selection is still occurring and what might the advantages of different blood groups be.
  
  Whether it was natural selection that drove the current distribution of the different groups based on contact with certain pathogens more common in one area than others, for example, or if it was just population migration and distribution patterns is still being studied and up for discussion.
  
  Thanks for this great question – it got me interested and reading about the subject for a while! 😉
- Laura Dixon answered on 22 Jun 2010:
  
  Different blood types were thought to have evolved due to mutations of the genes that determined blood type. So originally, there was one blood type and when a mutation occurred that was equally good as or better than the original blood type, these genes were passed on and eventually became another well established blood type.
- Hermine Schnetler answered on 22 Jun 2010:
  
  A study was conducted in 1950 that showed that given certain geographical places the dominant blood type was normally different. From there the researcher was able to establish the different blood types to different cultures:
  Type O = hunters, originating 30,000 years ago
  Type A = Cultivators 20,000 years old
  Type B = nomad 10, 000 years ago
  Type AB = enigma 1000 years ago

Question: What is the the evolutionary explanation for different blood groups?

Comments