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Irreversible cell differentiation -

The world of stem cell research is confusing enough to make anyone's head spin, but the idea of irreversible cell differentiation was widely believed until recently. Simply put, this is the idea that once a stem cell, which has the potential to become any other type of more specific cell, e.g. a skin cell, is unable to revert or change into any other cell.

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Irreversible cell differentiation -

This was widely accepted as fact until the 1990s, when cloning technology began to emerge and it was proven that differentiated cells could in fact still be manipulated. The cloning of Dolly the sheep (pictured) was a landmark victory in proving this new theory as fact.

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Spontaneous generation -

Aristotle, considered one of the greatest minds in all of history, wasn't always right. One idea of Aristotle's that didn't quite survive the test of time, although it was taken as fact for nearly two millennia, was that of spontaneous generation.

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Spontaneous generation -

This idea of spontaneous generation suggested that all kinds of complex organisms, such as flies, simply appeared out of the blue. They had no descendants and they didn't give birth, they just simply burst into existence out of nothingness. It wasn't until 1862 when French chemist Louis Pasteur proved beyond a shadow of a doubt that spontaneous generation was completely invalid as a scientific theory.

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Phrenology -

Phrenology, a practice once wildly popular in the 19th century that is now widely considered mere pseudoscience, claimed that an individual's personality, temperament, and demeanor could all be revealed through the measurements of one's head.

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Phrenology -

Phrenology was, unsurprisingly, based on suspect research to begin with, and was commonly used to legitimize the bigoted preconceptions of the time. Thankfully, phrenology's heyday was short-lived, and no one has taken phrenology seriously since the 20th century.

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Geocentric theory -

Today, it's common knowledge that the earth and the rest of our solar system's planets revolve around the sun. This widespread knowledge is thanks to the Renaissance astronomer Nicolaus Copernicus, who introduced his heliocentric theory to the world in 1453.

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Geocentric theory -

Before Copernicus, however, all of Europe and most of the world believed that not only the sun and the stars, but the entire universe, revolved around the earth, which was believed to be at the center of the universe. This completely inaccurate view of the universe, popularized by the Greek-Egyptian mathematician Ptolemy, was the accepted theory of the universe for over a thousand years.

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Phlogiston -

In the 17th century, the field of chemistry as we know it today, that is separate from ideas like alchemy and the Philosopher's Stone, was still relatively young, and creativity played a big role.

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Phlogiston -

In 1667, German chemist Johann Becher (pictured) suggested the existence of a substance called "phlogiston." According to Becher, phlogiston was to blame for fires, combustion, and rust. In order to put out a fire, all that was needed was to simply "dephlogisticate" it. About a century later, in 1774, Joseph Priestley's discovery of oxygen made the phlogiston theory immediately obsolete.

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The Piltdown Man -

The fiasco of the skull of the famed Piltdown Man all began in 1912 when the now-disgraced archaeologist Charles Dawson claimed to have found a skull from the ever-elusive "missing link" in human evolution.

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The Piltdown Man -

Nicknamed the Piltdown Man, the general public enthusiastically accepted this as the lost ancestor of humankind. Later, it was discovered that the Piltdown skull was in fact a medieval-age human cranium paired with the jaw of an orangutan. Today, the Piltdown Man is considered one of the greatest hoaxes in scientific history.

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The age of the earth -

Countless scientists throughout history have adjusted the earth's birthday, as more and more information came available. In the 1700s, a French scientist named Georges-Louis Leclerc estimated the earth was a relatively infantile 75,000 years old.

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The age of the earth -

From 75,000 years, the estimate grew significantly to 100 million years, a number put forth by Charles Darwin. Lord Kelvin (pictured), estimated the earth could potentially be as old as 400 million years, but he was wrong as well. Today, it is believed the earth is about 4.5 billion years old.

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The blank slate theory -

Widely respected in his time, English philosopher John Locke developed his theory of tabula rasa, or the "blank slate" theory. This theory suggests that humans are born without innate instinct or thought and that everything is learned from outside influences. It was the most pro-nurture defense in the argument of nature versus nurture.

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The blank slate theory -

Modern genealogists almost universally agree that certain innate instincts are in fact wired into the brain, as are certain personality traits that are passed on genetically.

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Einstein's Universe -

In 1917, one of the world's greatest minds, Albert Einstein, proposed an entirely inaccurate model of the universe that suggested the universe was in a perpetually stationary state, was neither contracting nor expanding, and never would.

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Einstein's Universe -

A little over a decade later, in 1929, American astronomer Edwin Hubble proved through his discovery of redshift that the universe was, in fact, expanding outwards at a constant rate.

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Planet Vulcan -

A century before Einstein's theory of relativity explained some of the greatest questions of the universe, a French astronomer named Urbain Le Verrier (pictured) was busy studying the orbits of the planets, and even deduced the existence and near-exact position of Neptune through pure mathematics.

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Planet Vulcan -

Unfortunately, Le Verrier's calculations weren't always so visionary. The astronomer also suggested the existence of a planet, dubbed Vulcan, orbiting between the sun and Mercury. No such planet was ever found, and the theory of relativity debunked the Vulcan theory for good.

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The growing earth theory -

Before the discovery of the tectonic plates and the advent of tectonics, Charles Darwin suggested that the disconnection of the modern continents was caused by a previously unified landmass being torn apart not through tectonic movements, but by the gradual growth of the earth.

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The growing earth theory -

As one of the most respected minds of his generation, most people adopted Darwin's hypothesis. It wasn't until the 1970s, when plate tectonics rose in popularity, that the growing earth theory was debunked.

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The creation of killer bees -

Killer bees, as much as many would love for them to be a hoax, are in fact very real. They were created, on purpose, by scientists in Brazil in the 1950s who thought that by breeding docile European honeybees with their more aggressive, but more weather-adjusted African cousins, they could craft a bee perfect for honey production in Brazil.

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The creation of killer bees -

Unfortunately, things didn't go quite as well as planned. While the cross-breeding of the bees was successful, they were just as angry as ever but preferred the climate of North America. It took some time, but by the turn of the century, these new and 'improved' killer bees were busy wreaking havoc across the Southwestern United States.

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The fen-phen diet -

Diet fads are always to be considered with a grain of salt, and diet pills even more so. One of the largest fads in the 1990s was known as the "fen-phen" diet. It was meant to combine two pharmaceuticals to create a miraculously fast and painless path to weight loss.

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The fen-phen diet -

The two drugs in question were fenfluramine, an appetite suppressant used to treat morbid obesity, and phentermine, a stimulant. Despite a glaring lack of any long-term studies to refer to, doctors began liberally prescribing the combination to anyone who requested it, until it was discovered in 1996 that the combination, used over the period of multiple months, caused a 23-fold increase in an individual's likelihood to develop pulmonary hypertension, a lung condition that can lead to death.

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The MTBE problem -

In the 1970s, gas and oil companies started putting methyl tertiary butyl ether, or MTBE, into gasoline. The idea was that the addition of MTBE would cut down on pollutants released by the burning of gas. Unfortunately, there were some unforeseen side effects.

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The MTBE problem -

Underground tanks of MTBE leaked at alarming rates across the country, and the substance, being extremely water-soluble, spread like wildfire and infected the water tables of numerous urban areas. Even in the 21st century, studies show that 14% of all urban water sources are affected by the fuel additive.

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The Milky Way as the entire universe -

One of the largest and most pressing questions of early 19th-century astronomy was just how big the universe was, and how far away from Earth were the strange, cloudy objects that we now know as nebulae. A large number of the scientific community believed that, whatever they were, those celestial objects must be at least within our galaxy, because our galaxy was the extent of the entire universe.

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The Milky Way as the entire universe -

As we now know, our galaxy is an incomprehensibly tiny speck in the vastness of the universe. It wasn't until the Shapley-Curtis debate, also called the Great Debate, in 1920, that the idea that the universe stretched on beyond our galaxy began to catch on.

Sources: (Cultura Colectiva) (Discover Magazine) (Science News)

See also: Scientists warn: Humanity faces the brink of self-destruction in 2024

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