This question already has an answer here:

What are the popular theories regarding how our blood divided into 4 groups. Particularly I'm interested in whether this was originally linked to disease.

Thanks for your answers, useful articles and further reading would also appreciated.


marked as duplicate by fileunderwater, Amory, Cornelius, WYSIWYG Sep 15 '15 at 18:45

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    $\begingroup$ Hi and welcome. Your question is very interesting, however, the general expectation of SE is that you demonstrate that you have researched the topic of your question and have hit a wall in that search, or you are looking for expert advice to explain an advanced topic that you have found that you are having a difficult time explaining. Review How Do I Ask a Good Question for tips and general expectations for the site. Though I personally hope someone can provide an answer as I would be interested in this as well. $\endgroup$ – AMR Sep 15 '15 at 13:11
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    $\begingroup$ Possible duplicate of biology.stackexchange.com/q/31920/3340 $\endgroup$ – WYSIWYG Sep 15 '15 at 13:15
  • $\begingroup$ yep, sorry for duplicating and thanks for your answers! $\endgroup$ – dshulgin Sep 16 '15 at 8:58