Origin, or source, of rhesus negative in human blood?

Question

I recently learned that I have Rh- blood (I'm A-), and was idly looking into blood types on Wikipedia. I was surprised to find that relatively few (~15% of all) humans have it, and most of those seem to be European. Looking just a little further, I found a bunch of crackpot-looking sites that try to explain how people got Rh- blood, and what weird abilities they possess as a result. I managed to find one site that seemed at least less laughable, which suggested that interbreeding with *Homo neanderthalensis* (or possibly *Homo sapiens neanderthalensis*, since the site seemed to indicate that there was some question about how different *H. s. sapiens* were from *H. neanderthalensis*) might have accounted for the introduction of the condition. It seems that from more reputable (medical) sources, the only difference between Rh+ and Rh- is that complications can arise during pregnancy if the mother is Rh- and the fetus is Rh+. Indeed, most sites (e.g., WebMD) seem to explicitly state that there are no other differences of note. I am not a biologist, or an anthropologist, or a life-science kind of guy at all. However, as a computer scientist, I like to think that I have both an open mind but one which demands scientific and/or logico-mathematical evidence for claims. Lots of the pseudo-scientific, paranormal, etc. theories on the web I basically dismiss out of hand, as explanations which are almost certainly fantasies, but most definitely baseless and untestable. My question: > What, if any, is the current scientific understanding of the origin, or source, of rhesus negative blood in human beings? Do individuals with Rh- blood have any common (in a statistically significant sense) characteristics or health issues, aside from the issue with pregnancy and tending to be more European than not? Is there anything to continuing to look into this?

Answer 1

When it comes to blood typing being positive or negative is not a condition. In fact, being Rh- just means that your blood cells don't have the antigen. The antigen is like a sign that says, "Hey I identify as this!" In your case your blood cells would say, "Hey I identify as blood type A!" versus "Hey I identify as blood type A +!" There are no significant medical conditions caused by not having the Rh factor antigen. Outside of pregnancy, the only other concerns would be for organ donation and blood transfusions. In your particular case you would be able to only receive blood from someone who is also negative. You could receive from A- and O- blood types. Since you are Rh- you could give to someone who is negative or positive. So your blood could be given to the following blood types: A-, A+, AB-, and AB+.