Nov 13, 2024 08:00:00

What are the results of searching for the primary source of the 'oldest lie on the Internet'?

There are many hoaxes and urban legends on the Internet that are spoken of as fact, and many of them have been forgotten about why they were spoken. The rumor that 'human blood vessels are long enough to circle the Earth two and a half times' is one of the oldest rumors on the Internet, spoken as if it were true, despite the source being unknown. Science YouTube channel

Kurzgesagt explains in an animated video why this rumor was born and whether it is true.

We Fell For The Oldest Lie On The Internet - YouTube


It is often said that one of the wonders of the human body is that if all the blood vessels in the human body, including capillaries, were connected together, they would reach a length of about 100,000 km, enough to circle the Earth two and a half times. In fact, if you Google 'blood vessels two and a half times the Earth,' you will find articles from various hospitals, universities, and media outlets that talk about this as trivia.

However, there are still many things we do not know about the internal structure of the human body. In

a feature article by the Keio University School of Medicine, a professor of anatomy said, 'The human blood vessels are said to be 100,000 km long, or two and a half times the circumference of the Earth. If you think about it, it's a strange phenomenon that they run through our bodies without being tangled at all. In fact, there are a lot of structures and functions that have yet to be elucidated.' In the midst of all this, Kurzgesagt pointed out that no one knew the source of how it was discovered that 'the blood vessels in the human body are two and a half times the circumference of the Earth.'

According to Kurzgesagt, among internet articles which say that 'the number of blood vessels in the human body is two and a half times the circumference of the Earth,' there are also many different details, with some saying that 'if all the capillaries were expanded, the length would be 100,000 km,' others saying that 'the combined length of arteries and veins is 100,000 km,' and still others saying that the combined length of both is 100,000 km.

So Kurzgesagt searched for the original source of the trivia that 'the blood vessels in the human body are two and a half times around the Earth'. However, even after referring to thousands of sites, blogs, and books, it was difficult to find the source because they all seemed to be referring to Internet articles and books as sources. Furthermore, Kurzgesagt tried searching '100,000 km of blood vessels in the human body' in

PubMed , a medical literature search database, but did not get a single hit.

In an attempt to find a source closer to the original, Kurzgesagt searched again for blood vessel length, specifying the time period '1990-1995.' This resulted in two books: ' Vital Circuits ' by Steven Vogel, a professor of zoology at Duke University, and ' Looking at the Body ' by David Suzuki, a professor of genetics at the University of British Columbia.

In particular, Suzuki is popular and well-known as a science program caster in Canada, so Kurzgesagt thought that the rumor may have spread from Suzuki's remarks. So, when he actually read 'Looking at the Body,' he found a statement in the text that read, 'If the blood in the human body were lined up in series, it would reach 96,000 km. This is a length that would allow you to go around the world two and a half times.' However, even here, no specific source was given. Kurzgesagt tried to ask Suzuki directly about the source, but he was told, 'It's a book from 30 years ago, so I don't remember the source.'

Vogel's 'Vital Circuits' also states that 'the length of blood vessels is 100,000 km, more than twice the circumference of the Earth at the equator.' Vital Circuits lists several papers as sources, and although it was difficult to find which source was which, Kurzgesagt came across a 1959 article in Scientific American, a long-established American scientific journal, titled 'La microcircolazione del sangue (Microcirculation of the Blood).' This was also not a primary source, but it does show the source of the data.

The source of Scientific American's information that 'blood vessels are 100,000 km long' is the 1929 book '

The Anatomy and Physiology of Capillaries ' by Danish biologist Professor August Krohg .

'The Anatomy and Physiology of Capillaries' is a book that records Professor Krog's lectures, in which he mainly outlines research that integrates ideas and hypotheses with experiments. One of them states, 'There are about 2,000 capillaries per square millimeter. Assuming the body of an adult male weighing 50 kg, the total length of the capillaries is about 100,000 km. If connected vertically, this is the length that would circle the Earth two and a half times, and if spread out horizontally, it would cover the surface of 6,300 square meters.' Kurzgesagt concludes that this is the primary source of the Internet rumor of an unknown source that 'the length of human blood vessels is two and a half times the Earth.'

However, Kurzgesagt points out that what Professor Krog calculated from his experiments may not be accurate by modern scientific standards. According to Kurzgesagt, the experiment analyzed muscle samples from various animals and then calculated an estimate of human capillary density, but the calculation is quite inaccurate. In addition, the calculation was based on a sample of a person with a fairly ideal body fat percentage and muscle mass, and it may be far from the data for an average adult male. The problem is that what Professor Krog showed as just an interesting idea and an example of a calculation method continued to spread for 30 years without being true or false, and the source became unclear at an early stage. In fact, a study that calculated similar data in 2021 estimated that the total length of capillaries is '9,000 km to 19,000 km', which is not even halfway around the earth.

Kurzgesagt summarizes, 'When you search for information on the Internet, you quickly find a likely answer. However, Internet articles, and sometimes even scientific papers, often do not cite primary sources and instead continue to cite secondary and tertiary sources. In such cases, the information becomes distorted little by little, with only easy-to-understand numbers or impactful expressions remaining. As we experienced this time, it can be extremely difficult to find the primary source, but it is important to pay attention to primary sources and their reliability in order to avoid falling into the traps of information and to gain better knowledge.'

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