The term “blue blood” refers to the supposed purity and nobility of royal bloodlines. It originates from the Spanish phrase “sangre azul,” meaning blue blood. There are a few theories as to why royal blood is described as blue:
Theory 1: Visible Blue Veins
One popular theory is that the phrase refers to the visible blue veins under the pale skin of Spanish and English royalty. Since royalty at the time were wealthy and not doing manual outdoor labor, they had lighter skin that made their blue veins more visible. This gave the impression that their blood itself was blue.
The blue blood theory first became popular in Spain, where the Moorish, Jewish, and Muslim populations had darker skin than the Christian royalty and aristocracy. Having very pale skin was a status symbol among Spanish nobility to differentiate themselves from other groups. This pale skin enhanced the visibility of blue veins.
Later on, the blue blood concept spread to Britain. The aristocracy there similarly had lighter skin than peasants who worked outdoors. So the visibility of their blue veins under pale skin perpetuated the myth that their blood itself was blue.
Theory 2: Mixing with Divine Blood
Another theory is that royal blood is blue because it is mixed with the blood of gods or holy figures. This myth reflects the concept of the “divine right of kings” – that royalty derived their power directly from divine blessing or ancestry.
In ancient civilizations, many kings and queens claimed descent from the gods or other divine figures. For example, the pharaohs of ancient Egypt claimed to be living gods themselves. And Roman emperors claimed descent from Venus, Mars, and other Roman deities.
This myth continued through the Middle Ages and Renaissance eras in Europe. Many royal families claimed ancestors like Jesus Christ, King David, Alexander the Great, or the gods and heroes of Greek and Roman mythology. Because they supposedly had divine ancestry, their blood was seen as sacred and blue.
Theory 3: Inbreeding Among Royals
Some believe that blue blood refers to the effects of inbreeding among royal families over many generations. Intermarriage between royal lines was very common for political alliances in Europe. The Habsburg family was especially known for frequent inbreeding.
Inbreeding condenses the blood – it reduces genetic diversity and increases the chance of recessive traits manifesting physically. One of these effects may have been a bluish tinge to the skin, making veins appear even more blue under the pale, translucent skin caused by inbreeding.
However, modern doctors reject this theory. While inbreeding does cause health issues, it does not actually turn the blood or skin blue. The bluish hue probably came more from the ultra-pale complexions of royalty who avoided outdoor labor and sunlight.
Debunking the Myth: Blood Is Never Blue
While these theories may explain the origins of the phrase “blue blood,” human blood is never actually blue. Blood gets its red color from the hemoglobin protein containing iron molecules.
The only exception is blood low in oxygen – but even this is a dark red or purple, not blue. Deoxygenated blood only takes on a blue appearance in diagrams, not in real life. So royalty do not actually have blue blood flowing through their veins.
What Gives Blood Its Red Color?
Blood owes its bright red color to the presence of hemoglobin, the protein that carries oxygen from the lungs to the body’s tissues through blood vessels. Hemoglobin contains iron, which binds to oxygen molecules. This iron gives blood its red hue.
When blood is oxygenated in the lungs, the iron molecules change shape to grab onto oxygen. This oxygenated form of hemoglobin makes blood appear bright cherry red. The blood maintains this color as it travels through arteries to distribute oxygen.
Once tissues extract oxygen from the hemoglobin, the molecules relax back into their deoxygenated shape. This form of hemoglobin has a darker, slightly purplish red color. The blood darkens as it returns to the heart through veins, ready to pick up fresh oxygen again.
Why Are Veins Blue?
Veins look blue because the surrounding tissue absorbs the red wavelengths of light from deoxygenated blood. The remaining bluish hue is what we see shining through the skin. But the blood itself remains red even inside veins.
Table summarizing why veins look blue but blood inside is still red:
| Vein Color | Blood Color | Reason |
|---|---|---|
| Blue | Dark red | Tissue scatters red light waves, leaving blue to reflect back to eyes |
So even though veins look blue from the outside, our blood remains different shades of red at all times.
Significance of the Blue Blood Myth
While blue blood itself is a myth, it powerfully represents the ideals of nobility, purity, and divinity associated with European royalty. Calling royal blood blue conveys how important bloodlines were to claims of authority during the Middle Ages and Renaissance.
Kings and queens went to great lengths to preserve the purity of their lineages. Marriage among royals was a carefully planned affair, intended to consolidate lands and bloodlines between different dynasties. The Habsburg dynasty especially became infamous for inbreeding that led to health issues and infertility, just to avoid marrying into other families.
The blue blood concept reinforced the rigid class hierarchies of the time. Nobles were seen as above commoners in all ways – including biologically. Peasants were told their blood was redder and coarser compared to the exalted blue blood of the aristocracy. This helped justify social inequality and upheld dynastic power.
So while blue blood is not real, it stands as a powerful cultural concept. The allure of blue blood ancestry persists today and is a recurring theme in popular media. For instance, author Brian De Palma directed a horror film titled Blue Bloods. And a drama series called Blue Bloods depicts a multi-generational family of New York policemen who come from a noble line of law enforcement.
These modern takes on blue blood convey the continued mysticism and privilege associated with noble heritage, even today.
Conclusion
In summary, royal blood is not actually blue. But the concept reflects how medieval societies venerated royalty as possessing special, almost magical properties in their lineage. Calling noble blood blue conveys notions of purity, divinity, and superiority over common people.
While biologically inaccurate, the idea of blue blood powerfully shaped social hierarchies for centuries. And it continues to represent aristocratic mystique and privilege in modern depictions of noble families, royalty, and dynastic power.