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

Question

This is my first post here, so please be gentle. 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? For context, I got started down this rabbit hole while looking into different dieting strategies, and found the "blood type diet". Just as an aside, I don't think there's a lot of merit to that diet... sounds like a fad thing. Any sources or information or help on this subject are appreciated.

Answer 1

The Rh factor is just another protein expressed (or not) on RBCs. It is only notable because of the response during subsequent pregnancy issue of an Rh negative mother to an Rh positive4 baby. Here's a quote from the internet:

Most people have never heard of the numerous other blood groups—such as the MN, Diego, Kidd and Kell—probably because they trigger smaller or less frequent immune reactions. And in some cases, like the MN blood group, humans don’t produce antibodies against the antigens. One “minor” blood type that does have medical significance is the Duffy blood group. Plasmodium vivax, one of the parasites that causes malaria, latches onto the Duffy antigen when it invades the body’s red blood cells. People who lack the Duffy antigens, therefore, tend to be immune to this form of malaria.