As humans have been learning more and more about blood types, they’ve used their newfound knowledge to determine everything from potential health risks and benefits, and even personality, solely based on one’s blood type.

One blood type in particular has caused quite a stir, especially on internet forums and social media posts. It’s Rh D-negative blood, often simply referred to as Rh negative blood.

So what is Rh D-negative blood? For starters, ‘Rh’ stands for “Rhesus”, an inherited protein found in red blood cells. The ‘D’ stands for “D-antigen”, one of the many antigens found in blood types; which is missing from Rh D-negative blood.

You might be asking yourself what’s the significance of having Rh D-negative blood. That’s a good question, and one that invites a variety of answers. The simplest answer is that Rh D-negative blood is rare. Within the US, it’s estimated that only 15 percent of the population has this specific blood type. One reason for its scarcity is the fact that many fetuses containing Rh D-negative blood are destroyed by their mother’s immune system and expelled from her body unless a doctor intervenes.

The most commonly held belief is that Rh D-negative fetuses are often rejected due to their incompatibility with their host’s blood type, in this case their mother’s. Some take this theory even further and theorize that the incompatibility is a direct result of Rh D-negative blood being extraterrestrial in its nature.

In layman’s terms, Rh D-negative blood could be a rare indicator of alien DNA according to some.

Allegedly, those with this rare blood type may have an above-average IQ, reddish hair, a heightened sense of intuition, and resistance to some parasites including toxoplasma.

Negative effects of having Rh D-negative blood are sensitivity to sunlight and high blood pressure.

More colorful allegations regarding Rh D-negative blood are that those who have it are more likely to report psychic abilities as well as encounters with and abductions by alien beings.

But is there any evidence to support the claim that Rh D-negative blood comes from an extraterrestrial source? The short answer is “no”. The long answer is “probably not, but maybe depending on your beliefs”.

For example, one of the theories that supposedly backs up the claim is that an extraterrestrial race known as the Anunnaki was highly influential in the building of ancient civilizations such as Mesopotamia and may have interbred with local populations, giving us Rh D-negative blood.

Another theory comes from religious texts such as the Book of Enoch, wherein stories are told of celestial beings descending from the heavens and mating with humans, resulting in hybrid offspring that supposedly carry the genetic markers for Rh D-negative blood.

Still, the popular consensus in medical science is that it’s simply a variation of a normal human gene. Most scientifically minded researchers would conclude there’s nothing extraterrestrial about Rh D-negative blood, and if there is then it would just be the result of extraterrestrials experimenting and manipulating human genes that already exist – not mixing it with their own genes nor introducing any alien genetic material to the equation.

The theory of Rh D-negative blood being alien in nature or otherwise inherited from the heavens has also raised concern that it could be a covert method of injecting a soft form of racism into scientific debate as most carriers of Rh D-negative blood are Caucasian.

Still, supporters of the alien-inspired theory often defend themselves against accusations of race-based motives in their assertions by countering with the fact that they also consider Rh-null blood, carried almost exclusively by Aboriginal Australian women, to be even rarer and more important to humanity as it is compatible with virtually every other known blood type. Some even consider it to be the “golden blood” that holds the key to all of humankind, while still maintaining that Rh D-negative blood is special in its own right.

Where does that leave us concerning the possibility that humans themselves are descendants of extraterrestrials? Well, to be honest, while the idea sounds romantic and alien theories are obviously a fun concept to indulge in, there just isn’t any conclusive evidence to currently support the hypothesis with or without the ethical concerns surrounding the debate.