Rh-negative blood is blood whose red cells lack the RhD protein, the main antigen of the Rh blood group system. Roughly 15% of people of European descent are Rh-negative, compared with about 1–3% in many sub-Saharan African populations and under 1% in East Asia. It is a common, inherited human variant, most often caused by the deletion of a single gene, RHD, on chromosome 1.
Rh status matters for two practical reasons: blood transfusion and pregnancy. Before the system was understood, an Rh mismatch could cause dangerous transfusion reactions and the loss of babies to haemolytic disease of the fetus and newborn. It has also become the subject of a popular belief that it marks a non-human, "Nephilim" or "Anunnaki" bloodline. This guide covers the biology, the medicine, the origins of that belief and how Billy Carson approaches the question.
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What is the Rh factor?
The Rh factor is a set of proteins on the surface of red blood cells, and in everyday use "Rh-positive" or "Rh-negative" refers to just one of them, the D antigen. The Rh system is large, with more than 50 antigens described as of 2023, but D provokes the strongest immune response, which is why it is tested routinely and attached to the ABO letter on a blood card (A-positive, O-negative and so on).
A person who carries the D protein is RhD-positive; a person whose red cells lack it is RhD-negative. Neither is healthier in daily life. The difference matters only when one type's blood meets the other's immune system, through transfusion or pregnancy.
How the Rh factor was discovered, and why "rhesus" is a misnomer
The Rh factor was identified between 1939 and 1940 through two lines of work that later converged. In 1939 Philip Levine and Rufus Stetson published a case report in the Journal of the American Medical Association, titled "Intra-group agglutination". A woman who had delivered a stillborn baby reacted badly to a transfusion of her husband's blood, even though the two were ABO-compatible. Levine and Stetson proposed that her fetus had immunised her against an antigen inherited from the father.
In 1940 Karl Landsteiner, who had discovered the ABO groups in 1901, and Alexander Wiener reported that serum from rabbits immunised with the red cells of rhesus macaques agglutinated the red cells of most humans. They named the reacting factor "Rh" after the monkey. The two findings appeared to describe the same thing, and the name stuck.
Later work showed the animal and human antibodies recognised different antigens. The factor detected by the monkey-derived sera was reclassified as a separate antigen, named LW in honour of Landsteiner and Wiener, while the human RhD protein kept the "Rh" label. So the "rhesus" in rhesus factor is a historical accident of naming. It does not mean Rh-positive people carry monkey blood, or that Rh-negative people lack it.
What makes someone Rh-negative?
A person is Rh-negative when neither of their two copies of the RHD gene produces the D protein. The gene sits on the short arm of chromosome 1, next to a closely related gene, RHCE, which codes for the other main Rh antigens (C, c, E and e). In people of European descent the most common cause of the Rh-negative type is a deletion of the entire RHD gene. In some populations, other variants that silence or weaken the gene are also found.
Because one working copy of RHD is enough to make the D protein, Rh-negative behaves as a recessive trait. Two Rh-negative parents will have Rh-negative children, while two Rh-positive parents can have an Rh-negative child if both carry one deleted copy. It is the same Mendelian pattern seen in many other common human traits.
Who has Rh-negative blood?
Rh-negative blood is found in every human population, but at very different frequencies. Standard references put it at about 15% among people of European descent, and around 17% in Britain. Surveys in the United States have reported figures close to 14%. In many sub-Saharan African populations the figure is roughly 1–3%, and in China, Japan, Korea and Indonesia it is under 1%; among Han Chinese it is 0.5% or less.
The highest frequency recorded anywhere is among the Basques of northern Spain and south-western France, where reported figures range from about 21% to 36% of the population. A 2018 study in the European Journal of Human Genetics by Flores-Bello and colleagues, which sequenced the Rh region in Basques and other populations, found the RHD deletion at a frequency of 47.2% of gene copies among Basques, the highest of any group studied.
That Basque peak is the most quoted fact in the "alien bloodline" literature. Geneticists read it differently: the Basques are a long-isolated population, and isolated populations often end up with unusual frequencies of ordinary variants.
Why does Rh-negative exist at all? The evolutionary puzzle
The puzzle is real and openly discussed by geneticists. Before modern medicine, an Rh-negative mother carrying Rh-positive babies risked losing later pregnancies to haemolytic disease, which should have pushed the RHD deletion down over time. Yet in Europe it stayed common.
Two main explanations have been proposed, neither fully settled:
- Genetic drift and founder effects. In small or isolated populations, chance can push a variant to high frequency. This is the usual explanation offered for the Basque peak.
- Balancing selection. Carrying one deleted copy might bring an advantage that offsets the pregnancy cost. Several studies have reported that RhD-positive heterozygotes appear protected against some effects of latent toxoplasmosis, a common parasite infection, but this remains a hypothesis.
The 2018 Basque sequencing study summed up the state of play: both demographic and adaptive processes have been suggested, but neither has been clearly demonstrated. What genetics does not suggest is an outside origin.
Rh-negative blood and pregnancy: what HDFN is
Haemolytic disease of the fetus and newborn (HDFN) happens when a mother's antibodies cross the placenta and destroy her baby's red cells. In the Rh form, an RhD-negative mother carrying an RhD-positive baby can be exposed to the baby's blood, usually at delivery, and begin making anti-D antibodies. The first pregnancy is usually unaffected; in later Rh-positive pregnancies those antibodies can cause anaemia, jaundice, swelling and, in severe cases, stillbirth or newborn death.
The condition was described long before it was understood; a French midwife's 1609 account of twins who both died, one swollen and one jaundiced, is often cited as the first description.
The turning point was Rh immune globulin, a preparation of anti-D antibodies given to the mother so that her own immune system does not become sensitised. In the United States it was introduced in 1968 under the brand name RhoGAM; the first injection was given in May of that year. William Pollack, John Gorman and Vincent Freda, who led the American work, shared the 1980 Lasker Award for it. With widespread use, the risk of sensitisation fell from roughly 16% of at-risk pregnancies to well under 1%, and Rh disease became rare in countries with routine antenatal care.
Blood group and antibody screening are now standard antenatal care. Anyone pregnant or planning a pregnancy who wants to know what their Rh status means should ask their midwife, obstetrician or doctor.
Rh factor and blood transfusion
For transfusion, Rh-negative patients should receive Rh-negative red cells wherever possible so they are not sensitised to the D antigen; Rh-positive patients can receive either.
That is why O-negative is known as the universal red-cell donor type. O-negative red cells carry neither A, B nor D antigens, so they can be given in emergencies before a patient's type is known, and blood services regularly appeal for O-negative donors. Plasma follows different rules, so "universal donor" applies to red cells only.
Where the "alien bloodline" claim comes from
The idea that Rh-negative blood marks a non-human lineage circulates widely in alternative-history books, websites, forums and online videos. It cannot be traced to a single author or founding text; it appears to have grown by repetition. Different versions attribute the bloodline to extraterrestrials, to the Nephilim of Genesis 6 and the Book of Enoch, or to the Anunnaki of Sumerian texts as read by ancient astronaut writers.
The arguments usually rest on three points:
- The Basque peak. Because the Basques are distinctive, they are presented as descendants of a separate lineage.
- The "monkey" name. Rh-positive people are said to share something with primates that Rh-negative people lack. As shown above, the monkey link was a naming mistake.
- The evolutionary puzzle. The unsettled question of why the variant stayed common is presented as a sign that it did not evolve on Earth.
The literature also lists traits said to be typical of Rh-negative people: an unusual body temperature, an extra vertebra, unusual sensitivity or psychic ability, and a tendency to red hair, green or blue eyes. None has been shown to be linked to RhD status in published scientific research. Some are simply common in the same regions where Rh-negative is common, a correlation of geography, not a cause.
What the genetics actually shows
Genetics treats RhD-negative as an ordinary human variant. Its main cause, the RHD deletion, has a known molecular basis; it sits beside a related gene that every human carries; and it occurs on every continent. Rh-negative and Rh-positive people routinely appear as siblings in the same family.
The uneven distribution and survival of the variant are genuine research questions. The existing explanations are terrestrial, testable and still being refined, and none of the evidence requires an outside source.
Billy Carson's reading
Billy Carson has addressed Rh-negative blood directly in videos such as "The Real Story Behind RH-negative Blood in Humans", published on the 4biddenknowledge Podcast Network channel, and "Alien Hybrid: Is Your RH Negative Blood a Sign?". In them he raises the question that many of his viewers ask: whether Rh-negative blood could be a marker of a hybrid lineage connected to the Anunnaki.
The question grows out of his wider reading of the Sumerian creation accounts. In his explanation of whether the Anunnaki created humans, Carson argues that the Mesopotamian texts describe genetic manipulation rather than magic, with Enki and Ninhursag combining their own material with early hominids. Readers who accept that reading ask whether any trace of it survives in human blood, and Rh-negative status is the trait most often proposed. The Rh discussion also connects to his work on the Nephilim of Genesis 6 and the Book of Enoch.
This page presents that as the question Carson explores, alongside the textbook biology above. The broader framework is set out in our guide to ancient astronaut theory, which also covers the main criticisms.
Watch, read and go deeper
Billy Carson's video "The Real Story Behind RH-negative Blood in Humans" is embedded on this page, and his fuller case for Anunnaki involvement in human origins runs through the 4BK TV series Anunnaki: Ancient Secrets Revealed. For the texts and debates behind the bloodline idea, start at the Anunnaki topic hub. For the health and body side of the site, the biohacking topic hub and our evidence-first guide to biohacking for beginners apply the same standard used here: what the claim is, and what the evidence shows.
Frequently asked questions
What does Rh-negative mean?
Rh-negative means a person's red blood cells do not carry the RhD protein, the main antigen of the Rh blood group system. It is most commonly caused by the absence of both copies of the RHD gene on chromosome 1. It is a normal human variant and does not affect day-to-day health.
How rare is Rh-negative blood?
It depends on ancestry. About 15% of people of European descent are Rh-negative, around 1–3% in many sub-Saharan African populations and under 1% in China, Japan and Korea. The highest reported frequency, roughly 21–36%, is among the Basques.
Is Rh-negative blood a sign of alien or Nephilim ancestry?
There is no scientific evidence for that. The idea circulates in alternative-history books and videos, drawing on the Basque peak and the "rhesus" name. Genetics shows RhD-negative is a known deletion found in every human population, with drift and possible selection as the leading explanations.
Can two Rh-positive parents have an Rh-negative baby?
Yes. Rh-negative is inherited recessively, so two Rh-positive parents who each carry one copy without the RHD gene can have an Rh-negative child. The chance in that case is one in four for each pregnancy.
Why does Rh status matter in pregnancy?
An RhD-negative mother carrying an RhD-positive baby can develop anti-D antibodies that harm a later Rh-positive baby, a condition called haemolytic disease of the fetus and newborn. Since 1968, anti-D immunoglobulin has prevented most cases where routine antenatal care is available. Anyone with questions about their own pregnancy should speak to their maternity provider.
Sources and further reading
- Philip Levine and Rufus E. Stetson, "Intra-group agglutination," Journal of the American Medical Association 113 (1939)
- Karl Landsteiner and Alexander S. Wiener, "An agglutinable factor in human blood recognized by immune sera for rhesus blood," Proceedings of the Society for Experimental Biology and Medicine (1940)
- Laura Dean, Blood Groups and Red Cell Antigens, National Center for Biotechnology Information (2005), chapters on the Rh blood group and haemolytic disease of the newborn
- Flores-Bello A., Mas-Ponte D., Rosu M. E., Bosch E., Calafell F. and Comas D., "Sequence diversity of the Rh blood group system in Basques," European Journal of Human Genetics (2018)
- Encyclopaedia Britannica, "Rh blood group system"
- Society of Obstetricians and Gynaecologists of Canada, clinical practice guideline "Prevention of Rh Alloimmunization"
These statements have not been evaluated by the Food and Drug Administration. This content is for information only and is not medical advice.
