Previous: 17 Unusual Historical Heists
Next: 28 Fascinating Facts About Time



View count:275
Last sync:2021-02-10 20:15
Evolution is a complex process. Natural selection, "survival of the fittest," that one image where the monkeys slowly turn into a human... what does it all mean?? Calm your Homosapien self down, we're here to explain everything you might have wrong about the theory of evolution.

Evolution still has its fair share of deniers. But even amongst its avid believers, there's still a lot of things people have backward. Join Justin Dodd as he breaks down some commons myths and misunderstandings about evolution.


Mental Floss is the home for all things curious. Subscribe here for new Mental Floss videos every Wednesday at 3pm (and don't forget the bell!):


 (00:00) to (02:00)

Survival of the fittest has become shorthand for Darwinism, but Charles Darwin didn't actual coin that phrase.

Herbert Spencer did, in his 1864 book The Principles of Biology, presenting it as his take on what Darwin called "natural selection". Instead of taking offense, Darwin actually embraced Spencer's terminology.

He even included it in the 1869 edition of The Origin of Species and praised it as a more accurate and convenient distillation of his evolutionary theory. But not every exchange of ideas regarding evolution has ended so amicably. Believe it or not, the theory of how life develops on Earth has inspired a lot of controversial and inaccurate statements, including some from Darwin himself.

That is why, I, your host, Justin Dodd, plan to settle the evolution debate once and for all in this episode of misconceptions. *chuckle* You're welcome, science. *Intro* "Natural selection" always means "survival of the fittest". Charles Darwin may have co-signed the phrase, but "survival of the fittest" is not an entirely accurate representation of natural selection. Natural selection is the process that weeds out disadvantageous traits from a population and allows advantageous traits to flourish.

Spencer's wording implies that surviving alone is enough for a specimen to propagate the next generation. This isn't true. Surviving to sexual maturity is one-half of the natural selection equation, and the other half is reproducing successfully.

A fish that's fast enough to evade predators won't have much impact on the gene pool if its eggs smell like shark nip. I don't think shark nip is a real thing, but you get the idea. This is why modern biologists prefer the phrase "reproduction of the fittest" over "survival of the fittest".

Still, this version can be problematic depending on how you interpret the word "fit". Spencer's phrase brings to mind animals that are, I don't know, stronger, bigger, faster than their competitors,

 (02:00) to (04:00)

we now know the specimens that are most likely to reproduce are always the ones that would do best in a one-on-one fight. Other traits, like cooperation, can be just as important to a population's success. No species better exemplifies this than human beings.

Humans are the most successful predators on Earth, despite being far from the strongest, or the fastest. Thanks to the evolutionary advantages of cooperation, I can get forty chicken nuggets delivered to my door without breaking a sweat. Ha. I think my ancestors would be very proud. Or horrified? I don't know, jealous, maybe?

Evolution is elegant. It's easy to view nature as a carefully designed masterpiece. Natural selection has produced some pretty incredible stuff, like the beautiful wood nymph moth, whose main defense mechanism is looking like bird poop. But for every bird poop moth, there are plenty of less elegant examples of evolution.

One is the inside of a giraffe's neck. In creating one of the most impressive adaptations in the animal kingdom, natural selection left behind a bit of a mess underneath the hood. The giraffe's brain is only ten centimeters from its voice box, but one of the nerves connecting the two parts is thirteen feet long. This is a gross oversimplification but, when a giraffe decides to vocalize, the impulse travels down the neck, around the aorta, and back up the neck again before reaching its destination.

That's because giraffes evolved from organisms that didn't have necks. Their distant ancestors were fish or fish-like creatures. In those animals, a nerve that wrapped around the heart may have made sense, but as giraffe necks have gotten longer, the configuration has gotten more absurd.

Sometimes, evolution's roundabout path results in something awesome. Take whales. You might assume that their phylogenetic tree starts and stops in the ocean, since that's where all life on Earth began, but fossil evidence shows that whales descended from terrestrial mammals roughly the size of wolves.

 (04:00) to (06:00)

That means that whales' ancestors left the ocean, adapted to walk on land, and then returned to the sea to evolve into some of the smartest and biggest creatures on Earth. It's not the most straightforward path to the top of the food chain, but they got there eventually.

Evolution is random. We've established that evolution isn't always elegant, but it's not exactly random, either. It's true that the genetic variations that drive evolution show up randomly in organisms, but once that mutation appears, natural selection becomes a lot more predictable. If a trait harms a species' chances for survival and reproduction, it won't stick around for very long. And if a trait helps its chances, it's more likely to spread throughout the population. Whether a trait helps or harms a given animal has everything to do with the environmental pressures a species faces.

Under certain conditions, some evolutionary traits are practically inevitable. We see this in a phenomenon called "convergent evolution". Bats and birds evolved wings independently, not through some freak coincidence, but because they faced similar demands from their ecosystem. So, no, Earth producing life that's well adapted to its environment is not the same as an immortal monkey typewriter eventually producing Shakespeare. Well, unless that monkey has help from like, a really good editing team, that saves the good stuff, burns the rest, I don't know.

There's a "missing link" in human evolution. Whether in reference to fossils or Bigfoot, you've likely heard the term "missing link". It's used to describe some mysterious, unknown creature that, if discovered, would draw a clear line between humans and our ape ancestors. But, as any evolutionary biologist will tell you, the whole concept is rooted in a misunderstanding about how evolution works. For there to be a transitional species connecting ancient apes to modern humans, evolution would have to unfold like a ladder, with one link leading clearly to the next. This line of thinking gave us the argument "If humans evolved from monkeys, why still monkeys?"

 (06:00) to (08:00)

It's also responsible for the iconic, but thoroughly unscientific, illustration known as the March of Progress, which actually never intended to show what people generally now assume it's showing, but that's a misconception for another time.

The counter to these misconceptions is that evolution is not a linear hierarchy. It's more like a messy web. Multiple lines can break off from one population. Populations can gain traits and lose them later, land mammals can turn into whales sometimes. Drawing a straight line from one species to another across millions of years is impossible. Even the idea of a transitional species come with problems. It implies that some species are fully formed evolutionary ideals, while others only serve to bridge gaps in nature's timeline.

The truth is that change is constant, even in humans. Wisdom teeth, for example, are vestigial features. It's estimated that 35% of the population is born without them, and that number may eventually grow to 100. That means, in like, a million years, your fossil could be held up as a link to a more primitive time in human history. Now you know how Lucy feels.

Wisdom teeth aren't the only defunct features humans have held on to. The tailbone and that little pink flap in the corner of your eye both no longer serve their original functions. By observing these traits in other animals, scientists can conclude what those functions used to be. Our coccyx once supported a tail, and our plica semilunaris used to be part of a third eyelid. These traits don't serve much of a practical purpose today, but they do demonstrate that losing features in evolution is just as typical as gaining them.

Evolution is just a "theory". This is true, but not in the way that it's often trotted out. The meaning of the word "theory" changes depending on the context. You may believe the theory that Avril Lavigne died in 2003 and was replaced by a look-alike, but that's not the same thing as a scientist promoting the theory of evolution. In science, a hypothesis is a possible explanation for a phenomenon

 (08:00) to (10:00)

that hasn't been proven yet. When numerous related hypotheses are tested and can be put into a logical framework of facts and fundamental laws, you can bundle them together into a theory. A theory is a valid explanation for evidence that's been gathered and tested according to the scientific method. Theories may change as new facts come in, but the facts themselves generally aren't up for debate.

So, no, a scientific theory isn't comparable to a hunch, or an idea, or even a Reddit thread comparing very compelling tabloid photos from the early 2000s. Given the inconsistent use of the word amongst laymen, and even some scientists, British biologist and outspoken critic of creationism, Richard Dawkins, suggests that a more elegant solution would be to bypass the word "theory" altogether. He argues that a more clear understanding would be conveyed if we simply called evolution a fact.

Evolution can't explain complex organs. Many evolution skeptics point to complex organs when arguing against the theory. Something like the eye, for example, seems like a perfect, fully formed feature, so it's hard to imagine it being the result of a process as gradual as evolution. The truth is that vision hasn't always been so complex. The first eyes were likely simple patches used to differentiate between darkness and light. As the millenia progressed, these structures slowly evolved to become more sensitive to stimuli around them.

It's also worth noting that the eyes we use today are far from perfect. The blood vessels in our eyes cross the surface of our retinas instead of running beneath them, which makes vision problems more prevalent. So the organs sometimes held up as the most perfect structure in nature is actually kind of a disappointment, depending on how you see it. I personally can't see it, cause I'm somebody who's very nearsighted. The fact that I've been reading this teleprompter without the help of my glasses should be held as a monumental achievement.

Your environment can change your genes. The genes we pass down to our children are the genes we're born with.

 (10:00) to (12:00)

That means reading a lot, or lifting weights before procreating won't have any impact on the inherited intelligence or strength of your offspring.

But that's not how Jean-Baptiste Lamarck viewed inheritance. Several decades before Darwin shared his theory, the French naturalist proposed that adaptations acquired within an animal's lifetime could be inherited by future generations. So if a giraffe stretches its neck hard enough, its offspring will be born with slightly longer necks according to Lamarck. Lamarckism has been rejected by scientists, but the idea that an animal's life has no effect on its inheritable traits may not be entirely true, either.

Recent research shows that certain environmental factors can "turn on" genes that were previously inactive. In one study, mice that were separated from their mother, an event we would call traumatic in humans, were shown to have heightened fear and anxiety as adults. More intriguingly, they had "altered DNA methylation patterns on stress-respone genes", and could pass those traits onto their offspring, who had not been subjected to the same trauma. There's also limited evidence that stressors, like smoking and malnutrition, can awaken inheritable traits in humans.

This area of study is called epigenetics. It may sound similar to Lamarckism, but epigenetics differs in a major way. Any genes that are activated by the environment were already present to begin with. In other words, animals can't make new genes appear out of sheer will. There's a lot we don't know about epigenetics, but that hasn't stopped pseudo-scientists from embracing the concept. So just be wary of anyone who promises they have "one weird trick for transforming your genome overnight." Unless you really believe that this is your superhero origin story, then go for it.

Thanks for watching Misconceptions. If you have an idea for a future episode, leave it in the comments below. Seriously, please, I am fresh out of ideas. And my boss will not accept any of my pitches, cause apparently they are

 (12:00) to (12:06)

literally "all just about Keanu Reeves"? I don't see the big deal.