Rhesus negative blood seems to be one of the pseudoscientific buzzwords that mystery-mongers exploit on the internet.
Going around and around the internet are memes-usually from people like Robert Sepehr (who claims to be an “anthropologist”)-about how there’s something significant about people who have a rhesus negative blood type. One of the memes claims that “Rh-negative appeared suddenly 35,000 years ago in Cro-magnon,” and pretends to ask provocative questions about “why an Rh-negative mother” would reject an “Rh-positive” fetus, etc. This one is from Sepehr and it closes with the bold statement that “humanity isn’t one race, but a hybrid species.” He fails to elucidate with what we are hybrid with. One is left to buy one of his fictional books that he strangely markets as non-fiction. I think there we might find he meant the Annunuki, the Nephilim, aliens, or [insert favorite god].
Background on Blood Groups
There are several ways of grouping blood. About 35 ways, actually. The two most people are familiar with are the ABO and Rh methods . This is where we get designations like “A Positive,” “B Negative,” “O Positive,” etc. The “Rh” comes from “Rhesus,” as in the Rhesus macaques that were initially used in studying the blood group. Beyond that, “Rhesus” is just a label.
The Rh blood groups have 49 antigens, but only D, C, E, c, and e are the most significant. The terms Rh positive and rhesus negative blood (Rh negative) refer only to the D antigen. A negative expression of the D antigen is caused by a deletion of the RHD gene. This happens in about 15% of Caucasian populations, about 8% in Black populations, and less than 1% in Asian populations. This distribution of occurrence is probably the source of Sepephr’s claim about it appearing “suddenly in Cro-magnon.” But we’ll look at this a bit more further in the article.
The Affect of RHD Deletion
The absence of the RHD antigen is problematic for someone receiving a blood transfusion. In the same way doctors must ensure a match between ABO groups (though being a recipient vs. donor can make a difference), it’s also important that Rh factor also be considered. Also, if a mother who is Rh-negative is pregnant with a baby that is Rh-positive, the mother’s immune system can attack the baby’s blood. This is because people who are Rh-positive have the D antigen in the red blood cells. People who are Rh-negative do not, and will produce antibodies that attack the Rh antigens as though they were foreign germs. This creates a sometimes fatal blood disease called erythroblastosis fetalis  in newborns.
Not a real mystery today. It was probably 100 years ago, but today there are treatments for pregnant women that are almost always effective. So
why does Sepehr pose the question, “why does the body of an Rh negative mother carrying an Rh positive child try to reject her own offspring?” I can think of only two answers to why Sepehr asks this: 1) he’s ignorant of simple human evolution and biology and lacks the research skills to conduct a proper literature review of a topic; or 2) he knows and is lying to his readers in order to create hyperbole and mystery where none previously existed in order to sell books. In either case, he is unworthy of the apparently self-applied labels “author” and “anthropologist.”
What is the origin of this (or any) blood group?
This is difficult to answer since there isn’t a method to travel time and do population-wide blood tests. However, we can make some inferences based on available evidence. If you remember, I noted that the distribution of the rhesus negative blood (the Rh-negative expression–or the deletion of the RHD antigen) is currently 15% among Caucasians, 8% among Blacks, and less than 1% among Asians. Recent studies in parasitology have actually shed some light on this very question.
In a 2008 study, researchers  found that individuals who had both the Rh-positive and the rhesus negative blood alleles showed no decrease in reaction times in spite of infection with Toxoplasma gondii. a protozoan parasite that is common throughout the world and impairs reaction times of those infected to a point that they have 2-6 times higher risk for traffic accidents. The hypothesis for this neurological effect is to increase the likelihood that the protozoan will be transmitted from a carrier (bird, mouse, or other mammal) to it’s preferred host, which is any feline species.
The study above (actually a set of studies) looked at 4 different population samples of almost 1000 people total (n=868). They were broken down by sex, Rh -/+, and whether or not they had the Toxoplasma gondii infection.
Overall, those that were Toxoplasma-free and also rhesus negative blood appeared to have quicker reaction times. Those that were positive for Toxoplasma gondii and Rh-negative showed some decreased reaction times. But for those that were heterozygous for the RhD allele, that is to say–those that had genetic alleles for both Rh-positive and Rh-negative expression, their reaction times were remained the same whether they were infected with Toxoplasma or not.
The results seemed to indicate that there is an evolutionary advantage for a population to have the RhD deletion within it. This isn’t dissimilar from other genetic expressions that are seemingly harmful to individuals, but can have some overall positive benefits to a population. The sickle-cell trait is one such expression. While it can cause anemia within individuals, a carrier that isn’t anemic can avoid malaria.
The authors of the study above suggest that the higher incidence of Rh-negative among Caucasions isn’t because of their skin color. It’s because of geography and the relatively recent migration of feline species to Europe. In Africa and Asia, where felines have been for longer periods, the populations have had the opportunity to obtain balance and more heterozygous expression. In Europe, where the common domestic cat has been only for the last 2,000 or perhaps 3,000 years or so, the RhD deletion is more homozygous–the genetic expression across a gene pair is the same: either positive or negative (DD or dd).
No Grandiose Mystery Involving Aliens, Gods, or Giants
Having rhesus negative blood is no more mysterious than having blue or green eyes in a world full of mostly brown. Or red hair. Or the ability to process starches better with increased amylase. Different cultures have genetic expressions that are more common than others, often because of some advantage it provides based on the environment they live in. Or the environment their ancestors lived in.
Blood type is determined by DNA and DNA changes with time within populations. Some changes are bad some are not. Some have no negative or positive affect. Positive changes that offer an organism favor within its environment ensure that it reproduces and get carried on to that organism’s descendants. Changes (mutations) that are harmful often don’t allow the organism to reproduce, so those changes don’t get passed on to new generations. Changes in DNA that are neither beneficial nor deleterious–or at least not deleterious enough to kill off an organism, will get passed on.
And this is one reason why the RhD-Toxoplasma researchers were curious about Rh-negative expression. Because it was clearly so harmful, yet also because it survived multiple generations for so long, they reasoned that it had to have some positive outcome for a population.
So, when you see people going on about being “Rh-negative” and being some sort of “hybrid,” you have to ask: what does that even mean?
References and notes:
- Dean, L. (2005). “The Rh Blood Group,” in Blood Groups and Red Cell Antigens. Bethesda, MD: National Center for Biotechnology Information. Found online at: https://www.ncbi.nlm.nih.gov/books/NBK2269/
- Novotna, M., et al (2008) Toxoplasma and reaction time: role of toxoplasmosis in the origin, preservation and geographical distirbution of Rh blood group polymorphism. Parasitology, 135(11), 1253-61.