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more. [♩INTRO] The highest permanent human settlement is
a tiny mining village called La Rinconada, in Peru, which is about
5,100 meters above sea level. Considering that some people start to get
altitude sickness at around 2500 meters, that’s pretty intense. Not everything on Earth is as restricted as
we are, though. You might have heard of the hardcore microbes
that can live at super high elevations or the deepest parts of the ocean. But there are surprisingly complex forms of
life that can survive in those places, too. They just need some extreme adaptations to
do it. The most immediate thing you’ll notice at
higher elevations is that it’s way harder to breathe. The higher you go, the less air pressure there
is. Your lungs struggle to take in oxygen, and
you can develop altitude sickness, where the lack of oxygen causes symptoms like
nausea, a rapid heart rate, and in severe cases, swelling
in the brain. Spend enough time up there, though, and your
body will start to adapt by producing more oxygen-carrying red blood
cells. Other complex animals, like mammals and birds, can have pretty similar problems. And yet, yaks regularly hang out at elevations
of 6,100 meters. To cope with that, they’ve evolved larger
chests, lungs, and hearts, as well as thick, shaggy coats to help deal
with the bitter cold. Researchers have also discovered a bunch of
changes to their genetic code that help them survive up there, like by controlling their body’s stress
response when they’re low on oxygen. Birds can go even higher. The bar-headed goose, for example, regularly migrates over the Himalayas at altitudes
up to 7,000 meters. And the highest known vertebrate ever recorded
is Rüppell’s griffon vulture. In 1973, two pilots flying at 11,000 meters, 2,500 meters higher than the top of Mount
Everest, made a sudden and terrifying discovery when
a bird got sucked into the plane’s engine, forcing
an emergency landing. Not a good day for anybody involved... We don’t fully understand how these birds
do it, but both the bar-headed goose and Rüppell’s griffon vulture have genetic
mutations that allow the hemoglobin proteins in their blood to hold onto more
oxygen. Researchers have also found that when they’re
low on oxygen, bar-headed geese can move more air in and
out of their lungs than any other species we’ve ever studied. Any higher and you start to get into the realm
of microbes. Bacteria, for example, have been found at
the tops of storm clouds and up to 15 kilometers above the surface
of the Earth. We don’t yet totally understand how they
survive, either, but it’s not too uncommon to find microbes
in some of the most extreme environments on Earth. It doesn’t take quite as many genetic changes
to adapt when you’re a super tiny simple organism. Funnily enough, the biggest problem for survival
at extreme depths is the same as at extreme heights, at least for mammals. You start running low on oxygen. The deepest a human has ever dived without
taking oxygen with them is about 250 meters, but that’s nothing compared
to some other mammals. Southern elephant seals can dive more than
2400 meters, and in 2014, scientists watched as a Cuvier’s beaked
whale dove 3000 meters below the surface. Since mammals have to breath air, they need special adaptations to dive that
far. For example, some species have more red blood
cells, can slow down their heart rate, or can temporarily shut down non-vital
organs like their kidneys. Some also have extra myoglobin, a protein
that stores oxygen in muscle cells. But these divers are just visitors. There are species of animals that spend their
entire lives in the deep ocean. In 2017, scientists found the deepest known
vertebrate: a pink, wiggly snailfish at over 8,000 meters down in the Mariana Trench, the deepest part of the ocean. The fish doesn’t have that oxygen problem
that whales and seals do, since it gets its oxygen directly from the water. But there is another problem: pressure. Water is heavy, and the deeper you go in the
ocean, the stronger the water pressure becomes. At 8,000 meters, the pressure is like having a cow sitting
on every square centimeter of your body. And not a small cow either... At that point, the pressure is so great it might actually destabilize the proteins
the fish’s body is made of. To compensate, biologists think the fish’s
tissues are full of a compound called trimethylamine N-oxide, or TMAO for short,
which can help stabilize proteins. TMAO is common in fish, and the deeper you
go, the more of it they tend to have. But even with this adaptation, this may be
the deepest fish we’re ever going to see. Researchers have calculated that beyond 8200
meters, fish would need so much TMAO to withstand
the pressure that their cells would be saltier than the
seawater around them. Except then more water would rush into the
cells through osmosis, and then they would explode, and you can see
why that would be a problem. And yet, we can go even deeper. In 2012, James Cameron, yeah, the guy who made Avatar and Titanic, visited the deepest part of the Mariana Trench
in a submersible. And even there, over 10,000 meters below the
surface, he was greeted by relatively complex life: giant, foot-long
crustaceans known as amphipods, sea cucumbers, and weird, gooey, shelled things
called foraminifera. There’s a lot we still don’t know about
the organisms that live in the deepest parts of the ocean. It’s one of the biggest habitats on Earth,
and yet it’s also the hardest to explore. But we do know that life is super adaptable. And with a collection of those amazing adaptations, complex life can exist at some incredible
highs and some very low lows. If you want to learn more about science, and of course you do, because you’re watching
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so what is the most complex life