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.


I have been looking a little more, and I stumbled across a paper entitled, "The influence of RhD phenotype on toxoplasmosis and age-associated changes in personality profile of blood donors" which looks at the effect of the Rh- trait on personality changes caused by toxoplasmosis (if you Google the title, you should be able to download). Using Cloninger's and Cattel's personality factors, they seem to show a variety of things, including (a) personality differences between Rh+ and Rh- individuals not affected by toxoplasmosis, and (b) different reactions to prolonged toxoplasmosis affection in Rh+ and Rh- individuals.

I didn't even know that parasites could affect your behavior; that seems frightening on the one hand, but on the other, it's fascinating if it's for real, especially since the incidence of toxoplasmosis is not insignificant in most people. Anybody who knows anything about this or who reads the paper and can help me understand what it's saying would be doing me a great favor to answer/comment/chat. Thanks!

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    $\begingroup$ The blood type diet is a bunch of junk. There is no scientific merit to its claims. Genetic differences could be matched to a diet, but those differences should map to genes relevant to metabolic diseases such as cardiovascular disease, type 2 diabetes and the like. A genetic variant in phenylalanine hydroxylase (PAH) can lead to phenylketonuria (PKU) and specific diets can, usually are, prescribed to alleviate (risk of) symptoms. See omim.org/entry/261600. $\endgroup$ Mar 21, 2012 at 15:52
  • $\begingroup$ @Larry_Parnell Yeah, that was my impression as well... blood type should have little to nothing to do with diet, and certainly the guy's reasoning seems to be pure fantasy. It seems like most named diets are fads, and that the best way to live healthy is to eat a varied diet of appropriate quantities of fresh, healthful foods, stay hydrated, and to get some exercise... common sense stuff. Still, I'm interested in the origin of Rh- (interbreeding? mutation?) and what other traits have been observed to be correlated to (not necessarily caused by) it. $\endgroup$
    – Patrick87
    Mar 21, 2012 at 16:00
  • $\begingroup$ For the blood type diet see this question on our sister site Skeptics.SE. $\endgroup$ Mar 21, 2012 at 16:10
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    $\begingroup$ You may wish to also see our question: Is there any advantage to one blood type over another? $\endgroup$
    – Rory M
    Mar 22, 2012 at 18:21

5 Answers 5


Your question has many questions in it.

As for the evolution of Rh factor, Blancher and Apoil (2000) attribute the high level of sequence similarity (92%) of the two RH locus genes, RHD and RHCE to a gene duplication event in the common ancestor of human, chimps, and gorillas. Their analysis of the cDNA from these genes revealed "complex recombination events" after the lineages split.

Basically the most recent common ancestor of apes had the "human" RH genes, which then differentiated after the lineages diverged. Duplicate and differentiate is a common theme in evolution.

As for why it's called rhesus antigen, that's just as experimental artifact:

The term "Rhesus antigen" was introduced by Landsteiner and Wiener, who found that rabbits (and later, guinea pigs) immunized with red blood cells (RBCs) from a rhesus monkey produced antibodies which agglutinated 85% of Caucasian blood samples (Landsteiner and Wiener 1940, 1941).

They probably weren't even correct about the antibodies being rhesus:

In conclusion, if the term "Rh" was coined by Landsteiner and Wiener because of the source of antigens (the rhesus monkey) they used to obtain anti-Rh in rabbits, it is highly probable that, in fact, they produced anti-LW antibodies.



The high proportion of Rh-negative persons in the European population could be connected with the fact that, until recently, big cats (the definitive host of Toxoplasma gondii) were practically not present here and thus toxoplasmosis was rare (and Rh-negative persons were at an advantage compared to the rest of the population). The low percentage of Rh-negative persons in Africa (less than 1%) could be related to the high prevalence of toxoplasmosis there, which often approaches 100%.



Lafferty suggested that because climate affects the persistence of infectious states of Toxoplasma in the environment, it helps drive the geographic variation in the parasite's prevalence by increasing exposure risk. The parasite's eggs can live longer in humid, low-altitude regions, especially at mid latitudes that have infrequent freezing and thawing. Cultural practices of food preparation such as rare or undercooked meats, or poor hygiene, can increase exposure to infection, as can having cats as pets. Lafferty added, "Toxoplasmosis is one of many factors that may influence personality and culture, which may also include the effects of other infectious diseases, genetics, environment and history. Efforts to control this infectious pathogen could bring about cultural changes." / this is why I feel rh- is a newer blood grouping due to the last ice age conditions. these were the conditions in nw Europe back then and the rh- trait has persisted in that area. it just all makes sense . you may also search out " congenital toxoplasmosis infection " and I believe you will find when a pregnant woman gets toxo infection the baby comes out with the same symptom ology as erythroblastosis fetalis, rhesus disease.this is why all pregnant women are cautioned to avoid cat feces and stay away from cat boxes where they defecate.

OPINION ? i'll have you know i'm 61 y old retired medical worker who has studied biology and etc my whole life . this opinion is not just anyone's . btw i'm o- myself /




RhD-positive subjects have been confirmed to be less sensitive to the influence of latent toxoplasmosis on reaction times than Rh-negative subjects. While a protective role of RhD positivity has been demonstrated previously in four populations of men, the present study has shown a similar effect in 226 female students. Our results have also shown that the concentration of testosterone in saliva strongly influences (reduces) reaction times (especially in men) and therefore, this factor should be controlled in future reaction times studies.


The observed effects of RhD phenotype could provide not only a clue to the long-standing evolutionary enigma of the origin of RhD polymorphism in humans (the effect of balancing selection), differences in the RhD+ allele frequencies in geographically distinct populations (resulting from geographic variation in the prevalence of Toxoplasma gondii), but might also be the missing piece in the puzzle of the physiological function of the RhD molecule.

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    $\begingroup$ Welcome to the site. You answers take heavily from quotes, which should be marked as such. Rather than three separate posts, why not try to combine them into a single post with some additional analysis or insights? $\endgroup$
    – kmm
    Oct 18, 2013 at 13:26

It's my opinion the rh antigen developed from toxoplasmosis infection. I only recently learned that this protozoan can actually insert its genes into a host's genome. Once it's in the genes, it can be passed in the germline. Toxoplasmosis can infect all primates, human and otherwise. Monkeys get it, and so do humans living in toxoplasmosis endemic places. The life cycle of toxoplasmosis is connected with mice and cats as an evolved survival strategy for the toxoplasmosis protozoan. There never were cats in northwest Europe, and that would explain why the people with ancestry from that area were never exposed to toxoplasmosis. I look for the rational biological explaination. One great clue to my thinking is I found a term used in some research writings, the text read "RH strain of toxoplasmosis". Yes they seemed to be doing experiments with the toxoplasmosis found in rhesus monkey.

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    $\begingroup$ Can you provide citations to back up your hypothesis? Opinion doesn't go very far. $\endgroup$
    – kmm
    Jun 29, 2013 at 23:23
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    $\begingroup$ I am pretty sure there were wildcats in northwest Europe. $\endgroup$
    – skymningen
    Aug 30, 2013 at 6:50

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