Evolution FAILS in the Human Body

Hey smart people, Joe here. Bodies. We’ve all got ‘em. Couldn’t live without ‘em! But why are they so dumb and unreliable?! I don’t know if it’s because I just got
over a sinus infection or because my wife just had knee surgery, or maybe it’s just
me getting older and hurting more… I’M A MILLENNIAL!!
but I have been noticing lately that the human body… it’s got a lot of problems. And this video is a big long rant about a
bunch of ‘em. I mean don’t get me wrong, humans are really
awesome. Look at all we can do! It’s just that, there’s so much about
our bodies that is flawed. Like, so many of our parts wear down or are
easy to break, and others look like Ikea furniture would look if you accidentally threw away
the instructions before putting it together… in that it basically functions, but you’re
pretty sure something’s backwards and somehow you have like three of those little twisty
things left over?! The great American poet John Mayer once said
“your body is a wonderland”, but I think he meant “your body is a blunderland”. From eyes that don’t work right and backs
that ache to needy diets and extra bones… what I’m saying is… sure, our bodies look
cool–especially if they’re wearing an awesome shirt–but who the heck designed
these things?! Well, no one did. We’ll get back to that, but first, instead
of talking about how great we are, let’s talk about some of our critical weaknesses. The first example… it’s staring right
at ya. I mean, I don’t wear these things to look
cool and smart. I mean, they do make me look cool and smart,
but I wear them because I can’t see! Like nearly half of Americans and Europeans
or nearly 7 in 10 people in Asian countries, my peepers don’t peep right. I’ve worn glasses since elementary school. Space shuttle. Nice! Very on brand, younger me. Anyway, before the invention of corrective
lenses a few centuries ago, people who couldn’t see just… couldn’t see. And back in our prehistoric hunter-gatherer
days, that could’ve meant starvation and death. Bad eyes, empty stomachs, you lose. Thing is, even if you don’t wear glasses,
you have eye problems. While looking at this image, cover your left
eye, and look at the dot while keeping your face centered in front of the screen. Slowly move closer or farther from your screen
and the cross will disappear. Did it work? Around 30 cm or 12 inches away works for me. Pretty weird huh? You can try it with the other eye too. Cover your right one, stare at the cross,
and move until the dot disappears. That’s your blind spot, and every animal
with a backbone has a blind spot in each eye because of how the eye is built. The light sensitive layer inside your eye
is filled with tiny cells called photoreceptors. They’re like little microphones. One end turn photons of light into electrical
signals, and the other end’s a wire that carries the signal away. Except our retinas are built so the cables
are pointed towards the light, like talking into the back of a microphone. The cables from all those little microphones
have to pass through a hole in the retina to get to the brain. And where that hole is, we have a blind spot. We just don’t usually notice it because
our brain lies to us and fills in the image. Why do we have it? Because at some point way back in evolution,
when our ancestors started to evolve the first light-sensitive tissues, that’s just the
direction the cells were facing. And later, when those patches morphed into
actual eyes, it was too late. The backwards pattern was already set. Evolution can’t suddenly flip a whole eye
around. It can only make tweaks to what’s already
there. But cephalopods–like octopuses, squid, and
cuttlefish–they don’t have a blind spot. This branch of animals evolved eyes completely
on their own, and in early octopus ancestors, the cables on all their microphone-shaped
light-sensing cells pointed toward the back, so their retina is unbroken. Am I saying that cephalopods have better eyes
than us? Mmm, yes. Point, cephalopods. And another point for having eight legs. Ok, enough about eyes! Why is there so much empty space in our skulls? You know I can take you off the set any time right? Watch it, globie. When we breathe, air enters our nose and passes
through four chambers called sinuses where the air gets warmed up, humidified, and filtered
by mucous membranes. The mucus then drains ure is plenty in YOUR
skullout and back down your throat to your stomach. Mmm, gross. That works pretty well for the sinuses on
top, they have gravity to help them. But the big ones behind your cheeks? They drain up. Up! And that difficult drainage is why humans
get so many head colds and sinus infections. You know who doesn’t get sinus infections? Dogs. Dogs and other animals that rely mainly on
smell tend to have elongated nasal cavities, which drain down and back with gravity, the
correct way. But as our ancestors became more dependent
on vision and less dependent on smell, our snouts got smushed up into our flat faces,
and now we have tiny noses and get sick all the time. If you accidentally eat some air, no biggie. You can just burp it out. But if you breathe in your food, you’re
gonna choke and maybe die. What’s up with that? It comes down to the fact that like most other
vertebrates, we breathe and eat through the same throat hole, another one of evolution’s
amazing bright ideas. But I once saw a bird swallow a fish as big
as its head. It did not die. If I did that, I would die. But snakes and birds can swallow huge meals
whole because their nostrils connect directly to their breathing parts without going through
the throat. Like an alternate breathing system. But in every mammal, we’ve just got the
one tube, and all that separates the digesting part from the breathing part is a little flap
called the epiglottis. Epiglottis open? You’re breathing. Epiglottis closed, you can eat or drink. Mess up that order, here’s how to do the
Heimlich maneuver. Now, lots of animals can choke. Even whales can choke if fish get stuck in
their blowholes. Yes, that actually happens. But humans are especially prone to choking
because our voice box, or larynx, has moved up so high in our throats. I tell ya, these throats were made for talkin’. Some languages even make vocal sounds using
the epiglottis, like in some African languages. That higher voice box has squished up the
swallowing parts of our throat so there’s not a lot of room for error. But on the plus side, we can yodel. So maybe we can call this bad evolutionary
trait a tie. So. Walking upright. Pros: We can run, kick a soccer ball, dunk
a basketball, do sports things with all the other balls, ride a pogo stick, surf, ice
skate, dance, and dance dance revolution. Cons: So many unique and painful ways to injure
ourselves. Some of your body’s joints are beautiful. I’m a huge fan of the jaw. And the hip? That ball, that socket. It’s like Michaelangelo sculpted it. But the human knee and ankle look like an
elementary school art project held together by rubber bands. Back when our ancestors walked on all fours,
they had twice as many limbs and muscles to carry their weight. But when they transitioned to walking on two
legs, it put a lot more stress on our knees and ankles. When you quickly change direction while running,
the anterior cruciate ligament is basically the only thing holding the two halves of your
leg together. It has basically no blood vessels, and if
you tear it, the only way to fix it is surgery, which we only invented like a hundred years
ago. I have personally known at least a dozen people
who have torn their ACL. If we were hunter gatherers or ancient hominids,
every one of them would probably be dead. I don’t even know why I’m laughing, that’s
horrible. And right under that is the Achilles tendon. Since we walk on the balls of our feet, that
tendon takes basically all the force of the lower leg like a big fleshy rubber band. If you tear that one, you also can’t walk. It’s maybe the most important tendon in
your body, so of course it sits there on the back of our leg completely exposed, waiting
for the person behind us at the grocery store to ram it with their cart or your mythical
arch nemesis to hit you with a poison arrow. This is not how you’d engineer bipedal legs
from the ground up. This is way too many weak spots for any crucial
structural system. But when the assignment was “turn an animal
that walks on all fours into a fancy dancing ape on two legs”, evolution had to work
with what it was given. Body parts are one thing, but evolution has
messed up our insides too. Like, we are really poorly cut out for eating. Pretty much every animal needs the same nutrients
in order to function. Stuff like amino acids, vitamins, a few minerals. But most animals make most of these things
for themselves. But we have to get a literal grocery list
of nutrients from our diet. Take “vitamins”. That’s what we call essential macronutrients
that we have to get from our diet to survive. Vitamin C, for example. More than half a dozen proteins need vitamin
C around to do their job. Without it, your bones get brittle, your tissue
breaks down, you just bleed. Oh, and your teeth fall out. Scurvy is no fun. Pretty important stuff, this Vitamin C! So of course, we can’t make any. At all. We have to get every bit we need from our
diet. Almost every animal on Earth makes their own
Vitamin C. My dog never has to drink orange juice. Neither does a cow, or a cat. But I do. Strangely, humans have all the genes necessary
to make vitamin C in our DNA. Yet somewhere in our evolutionary history,
in some ancestor of all primates, one piece of the vitamin C machinery mutated and broke,
and now we have to eat it or die, along with all these. Of the 20 amino acids we need to build proteins,
our bodies only make 11. Many animals can make all twenty, but we have
to get almost half from our diet. Needing to have ready sources of these essential
nutrients has placed restrictions on where and how our species could live, at least before
we could walk into any pharmacy and get them all in pill form. Pretty much everywhere you look, it seems
like our body has room for evolutionary improvement. Our teeth? Most people grow a third set of molars–wisdom
teeth–that won’t fit in their mouth and have to be removed. Do I need to mention the fact that a male’s
gamete producing organs sit dangerously exposed outside the body? And the pelvis? Most women can’t deliver a baby without
medical assistance because the human head is so large. Who came up with all these bad ideas? The answer, of course, is no one. Thanks to science, we know that the human
body isn’t engineered, or designed. It’s evolved. Everything is the way it is because it got
that way, making tiny tweaks to what was there before. That means that our backs hurt because we’re
walking upright with a spine that used to be horizontal. We get fooled and we fool ourselves because
our brains evolved in a different world than the one we invented in the past few decades. Sure, our bodies are full of parts that barely
get the job done, full of things that could be built way better. And that can be frustrating, sometimes even
painful. But nobody, and I literally mean “no body”,
is perfect. Because surviving isn’t about being perfect,
it’s about being good enough. It’s about being imperfect in the perfect
way. If you’re watching this today, then you
are good enough. Because you’re a survivor of a 4 billion
year story. Our flaws make us who we are, because evolution
and natural selection made us who we are. Flaws and all. Stay curious.


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