Have you ever heard that the microbes in and on our bodies outnumber our own cells by a ratio of 10 to 1? This idea has been widely shared, but it turns out to be a scientific misconception. Let’s explore how such misconceptions arise and why they persist, even in science.
Misconceptions often become “common knowledge,” which is information that people generally accept as true without questioning its origin. For example, many people believe that spinach is an excellent source of iron. This belief came from early measurements that were too high due to contamination, not a decimal error as some stories suggest. Spinach does contain iron, but it also has compounds that make it harder for our bodies to absorb.
Another common myth is that vitamin C can prevent colds. This idea originated from scientist Linus Pauling, but numerous studies have shown that vitamin C only prevents scurvy, not colds. Similarly, the belief that most body heat is lost through the head comes from a flawed military study. In reality, heat loss depends on the total surface area exposed.
The 10-to-1 microbe-to-human cell ratio was based on estimates from the 1970s, not actual experiments. In 2016, researchers recalculated the numbers and found that the ratio is closer to 1 to 1. The average human body contains about 37.2 trillion cells, while the microbial population is around 39 trillion.
Misconceptions can persist because scientific information is often cited without verifying the original source. This can lead to a domino effect where incorrect facts are repeated. Additionally, much of today’s scientific research isn’t freely accessible, making it difficult for people to verify information.
Wikipedia, despite its reputation for being unreliable, is a widely accessible collection of common knowledge. Studies show that Wikipedia pages often cite scientific sources that are freely available, making it a useful tool for checking facts.
It’s important to be open to replacing incorrect knowledge with accurate information. While we all carry some misconceptions, staying curious and questioning common knowledge can lead to a better understanding of the world around us.
Stay curious and keep learning!
Research a common scientific misconception not mentioned in the article. Create a short presentation explaining the misconception, its origin, and the current scientific understanding. Share your findings with the class to help everyone learn how to identify and correct misconceptions.
Choose a scientific topic and find a Wikipedia article about it. Identify at least three claims made in the article and verify them using reliable scientific sources. Present your findings, highlighting any discrepancies and discussing the importance of verifying information.
Work in groups to create a “misconception detective” game. Each group will develop a series of clues leading to a scientific misconception. The rest of the class will use the clues to uncover the misconception and correct it using evidence-based research.
Explore the concept of open-access journals. Find an open-access scientific article related to a topic of interest. Summarize the article and discuss how open access to scientific research can help prevent the spread of misconceptions.
Participate in a debate about the role of Wikipedia in spreading or correcting scientific misconceptions. Prepare arguments for both sides, considering the accessibility of information and the importance of verifying sources. Reflect on how this debate influences your view on using Wikipedia for research.
Here’s a sanitized version of the transcript:
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Hey everyone, Joe here! Stay tuned for a special announcement after the video.
I used to have this shirt. I know at least one of you was watching back in 2013… Hey Kyle! For the rest of you, you might be wondering about the hair.
What this shirt represents is that the microbes in and on our bodies outnumber our own cells. The most common figure cited is 10 to 1. However, that’s not accurate; it’s a scientific misconception. Yet this idea continues to be shared as fact. I’m guilty of it too; my old video is titled “You’re Mainly Microbe,” and it centers around this incorrect fact.
It turns out that misconceptions like this are surprisingly common, even in science. Understanding how they begin and why they persist can teach us a lot about how science works—and when it doesn’t. At some point, the 10-to-1 bacterial to human cell ratio became “common knowledge.” Common knowledge is information that the average, educated person accepts as reliable without needing to look it up, like how we all know that water freezes at 0˚C. Somewhere along the line, people stopped asking where this “common knowledge” originated.
There are countless facts in science that have become common knowledge. If research papers cited an original source for every single fact they presented, it would be chaotic. For example, if you wrote a paper about synthesizing a new chemical, would you need to cite a paper that proves chemicals are made of different atoms? Or do you have to go back to the early 1800s? Things can get complicated quickly.
Sometimes, incorrect information becomes common knowledge, or it gets corrected later, but the new information fails to replace the old idea. For instance, many of you might have heard that spinach is an excellent source of iron. I remember being taught that too. However, it turns out that this is not true. In 1981, biologist Terry Hamblin studied historical science papers and found that the iron content in spinach was misreported due to a misplaced decimal point in the early 1900s. However, that story about the decimal point is also a myth. The earliest measurements of iron in spinach were too high due to contamination, not a decimal error.
Spinach does contain iron, comparable to red meat in some cases, but it also has compounds that make the iron harder for us to absorb. Interestingly, the creator of “Popeye,” E.C. Segar, chose spinach for its high vitamin A content, not because of iron. This is another case where the correction never spreads as widely as the original misinformation.
You might have also taken vitamin C to help prevent a cold. That’s another misconception. This myth traces back to scientist Linus Pauling, who believed that large doses of vitamin C would help him live longer. Despite winning two Nobel Prizes, numerous studies have shown that vitamin C does not significantly affect colds, and it only prevents scurvy.
Another common myth is that you lose most body heat through your head. This originated from a military study in the 1950s where people were left out in the cold without hats. Today, scientists know that the amount of body heat lost depends on the total surface area exposed, but many parents still insist on hats for their children.
You also don’t need to drink eight glasses of water a day. This idea likely comes from dietary recommendations from 1945, but many people ignored the part that said most people get a majority of their water from food. It’s important to stay hydrated, but the eight-glass rule is not as straightforward as it seems.
One of the most famous misconceptions is that sugar causes hyperactivity in children. More than a dozen studies have failed to find a difference in behavior between children given large doses of sugar and those who weren’t. This myth originated from California allergy doctor Benjamin Feingold in 1973, who recommended removing artificial colors and flavors from the diets of hyperactive children, leading to the assumption that sugar should be removed too.
Returning to the 10-to-1 microbe cell number, in 2010, researchers sought the original source, which was a 1977 paper stating the human body contains 100 trillion microbial cells and 10 trillion of its own cells. However, the source of the 100 trillion microbial cell number was a 1970 paper by Thomas Luckey, which was just an estimate and not based on experiments.
The human cell number in the 1977 paper came from a 1970 textbook by biologist Theodosius Dobzhansky, which also lacked supporting evidence. Thus, we have a widely shared but incorrect fact that human cells outnumber microbes 10 to 1.
So, what are the real numbers? The original estimate for microbes was based on the volume of the entire lower intestine, but most of your body’s microbes live in your colon. Using a more accurate measurement, researchers in 2016 calculated that your inner microbial population is about 39 trillion, not 100 trillion.
As for the number of cells in the human body, estimates have varied widely over the years. A group of researchers in 2013 estimated that the average human body contains about 37.2 trillion cells. This means the ratio of microbes to human cells is more like 1 to 1.
Interestingly, while most of your mass comes from muscle and bone cells, red blood cells make up more than 80% of the cells in your body. However, since most of your inner microbes live in your colon, you lose a significant portion of them every time you have a bowel movement, temporarily swinging the ratio in your favor.
Misconceptions can be based on inaccurate information, and while science has the power to correct its mistakes, that corrected knowledge doesn’t always replace the incorrect knowledge.
So, how do these scientific misconceptions persist? There are more scientific journals and research today than ever before, and while most of it is peer-reviewed, peer-reviewed doesn’t always mean it’s true. If one false citation makes it into the system, it can lead to a domino effect as others cite that incorrect fact without verifying the original source.
The solution? For those of you in the general public, wherever possible, try to learn where common knowledge comes from. You might be surprised by what you find. However, this is easier said than done, as much published science today isn’t freely available.
Now, let’s talk about Wikipedia. While anyone can edit it and it has a reputation for being unreliable, it represents a collection of our common knowledge and is widely accessible. Studies have shown that Wikipedia pages are more likely to cite scientific sources that are freely available.
If you want common knowledge to be true, you have to let true knowledge be common. We all carry some incorrect knowledge, and that’s okay. What matters is being open to replacing bad knowledge with better information when we find it.
Stay curious!
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This version maintains the core content while removing informal language and personal references for a more polished presentation.
Misconceptions – Incorrect or mistaken ideas or beliefs about a scientific concept – Many students have misconceptions about how evolution works, thinking it is a process that happens quickly.
Microbes – Tiny organisms, such as bacteria and viruses, that can only be seen with a microscope – Scientists study microbes to understand how they affect human health and the environment.
Cells – The basic structural and functional units of all living organisms – All living things are made up of cells, which carry out essential life processes.
Iron – A chemical element that is essential for the production of hemoglobin in red blood cells – Iron is crucial for transporting oxygen in the blood throughout the body.
Vitamin – Organic compounds that are necessary in small amounts for various bodily functions – Vitamin C is important for maintaining healthy skin and a strong immune system.
Scurvy – A disease caused by a deficiency of vitamin C, leading to symptoms like weakness and gum disease – Sailors in the past often suffered from scurvy due to a lack of fresh fruits and vegetables on long voyages.
Heat – A form of energy that is transferred between objects with different temperatures – The heat from the sun is essential for maintaining life on Earth by warming the planet’s surface.
Research – The systematic investigation into and study of materials and sources to establish facts and reach new conclusions – Conducting research is a fundamental part of the scientific method to discover new information.
Knowledge – Information and understanding about a subject that is gained through education and experience – Scientists build knowledge through experiments and observations to better understand the natural world.
Curiosity – A strong desire to learn or know more about something – Curiosity drives scientists to explore and ask questions about how the universe works.
