15 Outdated Scientific Beliefs That Shock Us Today
From flat Earth theories to bloodletting, explore 15 shocking outdated scientific beliefs that were once accepted as truth—until groundbreaking discoveries shattered them.
- Alyana Aguja
- 5 min read
Over time, most science theories previously taken for granted currently look downright remarkable. From Earth being the center of the universe to spontaneous generation, these scientific beliefs guided our comprehension of the universe for ages. Today, through revolutionary innovations and discoveries, we can behold how far human history has brought us in unwrapping secrets in nature.
1. The Earth is the Center of the Universe
Image from Britannica
Scientists long believed the Earth was the fixed center of the universe, with all other bodies revolving around it. The geocentric model, advocated by Ptolemy, reigned supreme for over 1,400 years. It wasn’t until Copernicus suggested the heliocentric model in the 16th century that humanity became aware the Earth orbits the Sun.
2. Spontaneous Generation
Image from Britannica
Before the 17th century, humans thought life could spontaneously emerge from dead matter. The perception that maggots grew from decaying meat or mice developed from heaps of grain was prevalent. Louis Pasteur’s experiments during the 1800s put to rest spontaneous generation, demonstrating that life originates from previously existing life.
3. The Four Humors Theory
Image from Wikipedia
Ancient Greek medicine was founded upon the assumption that the body contained four humors: phlegm, blood, yellow bile, and black bile. These humors needed to be balanced to create a healthy temperament. Now, we know that diseases are caused by pathogens, genetics, and many other causes—not by the imbalance of body fluids.
4. Miasma Theory
Image from Wikipedia
Before germ theory was established, people believed diseases like cholera and malaria were caused by “bad air” or miasma, stemming from decaying organic matter. This theory persisted well into the 19th century. The discovery of bacteria and viruses showed that pathogens, not foul-smelling vapors, were the true cause of disease.
5. The Continent of Atlantis
Image from HISTORY
Ancient Greek philosopher Plato described a mighty civilization called Atlantis that had allegedly sunk into the ocean. The myth was widely believed to be founded on historical facts, and some even suggested that Atlantis existed as a real place. With the advent of modern archaeology, though, no evidence has been found regarding the existence of such a civilization.
6. Phrenology
Image from Britannica
Phrenology was a belief system in the 19th century that the shape and contours of one’s skull could determine one’s personality and intelligence. Scientists and physicians used this pseudoscience to “measure” criminal tendencies, among other things. Today, we know that personality and intelligence are far more nuanced and cannot be measured regarding skull shape.
7. The Static Universe
Image from Wikipedia
Scientists believed that the universe had been static forever. According to this concept, which was driven by Isaac Newton’s laws of motion, it was assumed that the universe always existed in the same state. Edwin Hubble’s discovery that the universe was expanding in the 1920s broke that concept, establishing that galaxies were moving away from one another.
8. The Earth is Flat
Image from Physics World
Although ancient Greece discarded the concept of a flat Earth, numerous people still believed in this during the Middle Ages. This continued to be believed until explorers such as Christopher Columbus and Ferdinand Magellan proved that the Earth is a sphere. Satellite imagery today has given conclusive proof of our world’s roundness.
9. Bloodletting Heals Illness
Image from Wikipedia
Bloodletting was a general cure for many illnesses, including infections and fever, on the theory that it would restore the balance of humors. Bloodletting lasted thousands of years and was usually performed by barbers or doctors. Now we know bloodletting is not beneficial but rather detrimental, and medicine nowadays depends on vaccines and antibiotics.
10. Luminiferous Aether
Image from Wikipedia
Scientists in the 19th century thought that space was full of a mysterious medium named “aether” and that light waves propagated through it just like sound waves propagated through air. This explanation was prevalent until Albert Einstein’s relativity theory demonstrated that light propagates without the help of a medium. The idea of aether was abandoned, and physics developed by leaps and bounds.
11. The Missing Link
Image from Live Science
Before the theory of evolution was completely understood, most scientists assumed that there had to be a “missing link” between apes and humans. This led to the quest for one transitional fossil that would link us with our primate ancestors. Nowadays, we are aware that human evolution is a multifaceted process with numerous transitional forms, not one “link.”
12. The Empty Organ
Image from BetterKids
For many years, the appendix was considered to be a vestigial organ that was useless and had no function. It was widely assumed to be a remnant structure of our evolutionary predecessors. Current research indicates the appendix has a function in immune system function and gastrointestinal health, especially in early life.
13. Lamarck’s Theory of Inheritance of Acquired Traits
Image from Fiveable
Jean-Baptiste Lamarck suggested that acquired characteristics, such as a giraffe’s long neck extending so that it can reach leaves higher up on trees, are inherited by offspring. The theory of “inheritance of acquired traits” was popular before Darwin’s natural selection. Now, we understand that genetic inheritance takes place through DNA and not through acquired traits.
14. Eugenics
Image from Nature
In the early 20th century, eugenics was a belief popularly advocated for the idea that selective breeding could improve humanity. Eugenics was supported by many influential scientists and politicians, resulting in forced sterilizations and other forms of discriminatory treatment. We now realize the unethical and dangerous consequences of eugenics, and genetic diversity is now realized as being vital to the survival and health of populations.
15. Static Species
Image from Live Science
It was previously thought that species were permanent and unalterable, having been formed in their present form and staying that way throughout time. This belief was dispelled by Charles Darwin’s theory of evolution, which proposed the concept of species evolving over time by natural selection. Contemporary biology has established that species are dynamic, with genetic mutation and environmental pressure causing ongoing evolution.