The nature of blood and its connection to life has always fascinated humanity. In this article, we explore how different eras have understood the role and function of blood.
A History Written in Blood
The surface area of the human body’s blood vessels is approximately 700,000 square meters. Their total length is seven times the diameter of the Earth. Every day, around 100,000 heartbeats pump blood through this vast network.
Today, we know precisely that one cubic millimeter of blood (excluding plasma) contains around 5 million red blood cells, 7,000 white blood cells, and 300,000 platelets. However, our knowledge of blood has not always been this accurate.
What Is Blood?
The relationship between blood and life has always intrigued people. Blood has long been regarded as a source of life, as well as a symbol of inheritance and identity.
Until the 17th century, neither physicians nor scientists understood how blood circulates in the human body. It was believed that the lungs were responsible for circulation.
It was William Harvey who discovered that the heart is at the center of circulation. When he published his findings, however, his contemporaries simply mocked him. This reaction is less surprising when we consider that beliefs about blood date back to ancient times.
Ancient Times: The Divine Power of Blood
In ancient cultures—such as those of the Egyptians and Greeks—blood was believed to possess divine power. It became a symbol of both life and death.
The Egyptians revered blood as sacred, believing it was given by the gods to prolong life.
The Greeks considered blood to be the carrier of the soul, believing that the human soul resided within it.
The Middle Ages: The Magical Power of Blood
During the Middle Ages and the early modern period, blood was used in many magical and religious rituals.
In Christianity, blood symbolized the sacrifice of Jesus Christ, and the Holy Grail was associated with his blood. During this time, a wide range of superstitions and mystical beliefs surrounded blood, closely tied to both religious and secular traditions.
Eastern Cultures: Blood as a Marker of Personality
In Japanese culture, blood has been attributed with unusual characteristics. According to popular belief, a person’s blood type reveals their personality traits and compatibility with others.
This phenomenon is not limited to Japan; it is also popular in South Korea and Taiwan. The theory regained popularity in Japan in the 1970s through the work of Masahiko Nomi, although it lacks any scientific foundation.
Blood in Healing
Many cultures believed that blood had healing properties.
So-called “medicinal cannibalism” was not uncommon in the past. It was widespread across Europe and even known in royal courts.
At public executions, crowds would gather and push toward the front. It was believed that coming into contact with the blood shed during beheadings could cure illnesses.
Blood Sacrifice
The history of blood sacrifice is deeply rooted in human culture. In ancient rituals, people were sacrificed to honor the gods or to ensure fertility and abundance.
In Viking culture, being chosen as a blood sacrifice was considered an honor, and individuals accepted death with pride.
Such practices were not unknown in Hungary either. During the construction of new houses, certain rituals were widely known. The ballad of Kőműves Kelemen is not merely fiction—these sacrifices were known as “foundation sacrifices.”
Modern Times
With the advancement of medical science, our understanding of blood has evolved significantly. During the Renaissance and the modern era, scientific approaches came to the forefront. The discovery of blood circulation fundamentally changed how we understand the human body. Vaccinations and blood transfusions revolutionized medical treatments and contributed to increased life expectancy.
Advances in genetic research and genomics have made it possible to better understand the hereditary significance of blood and related health risks. At the same time, various religious and cultural traditions around the world continue to attribute additional meanings and roles to blood.
What Determines the Color of Blood?
Understanding what determines the color of blood is essential to understanding how the human body functions. Healthy blood is typically bright red or dark red, depending on its oxygen content. Oxygen-rich blood found in arteries is bright red, while oxygen-poor blood flowing through veins is darker.
But what exactly determines the color of blood? It depends on a protein called hemoglobin, found in red blood cells, which is responsible for transporting oxygen. When hemoglobin binds oxygen in the lungs, it becomes bright red. When it releases oxygen to the body’s cells, its color turns darker red. Therefore, the color of healthy blood depends on oxygen levels and the state of hemoglobin.
The color of blood can also indicate overall health. For example, pale blood may suggest anemia or other health issues. That is why regular blood tests are important—they can help detect and treat medical conditions at an early stage. In this sense, the color of healthy blood not only reflects oxygen levels but also provides valuable insight into overall health.
