What if Humans Were Cold-Blooded Creatures? Humans can live almost anywhere on the planet. We’re capable of adapting to the harsh conditions
of the arctic circle, the high altitudes atop the Andes, and even in the midst of tropical
jungles. In fact, few species are spread as far and
wide as humankind, with us even aiming to venture to the stars and colonise alien worlds. But could evolution have taken us down a totally
different path? This is Unveiled, and today we’re answering
the extraordinary question; What if humans were cold-blooded creatures? Are you a fiend for facts? Are you constantly curious? Then why not subscribe to Unveiled for more
clips like this one? And ring the bell for more fascinating content! First off, what do we actually mean by “warm”
and “cold-blooded”? Neither are the best nor most specific of
terms. Biologists would rather speak of “endothermic”
and “ectothermic” creatures, referring to animals that either produce their own body
heat, or don’t. As well as that, we have “homeothermic”
or “poikilothermic” creatures, meaning an animal either maintains its own internal
body temperature, or it relies on its environment to regulate it. All told, as humans, we’re endothermic homeotherms,
because we produce our own body heat and maintain it ourselves, through our metabolism. Most other mammals and birds also do this,
but cold-blooded animals – or “ectothermic poikilotherms” – are incapable of regulating
their own temperature. That’s why you see lizards in the desert
bathing in the baking sunlight, because they need to warm up their bodies before their
muscles and brains can work. Interestingly, though, even these aren’t
the only options that the natural world can throw up. Palaeontologists now believe that some dinosaurs
were actually “mesothermic”, meaning that they survived via a combination of creating
and maintaining their own body heat and utilising their environment. But for this video, let’s just focus on
the basic, non-dino categories. If humans had evolved to be cold-blooded instead
of warm-blooded, or even if we all miraculously turned cold-blooded overnight, one of the
first big changes we’d all notice is we’d be eating less food. A lot less food. Even the so-called ‘king of reptiles’,
the crocodile, can actually go more than twelve months without eating anything at all. They’re painted as ruthless killers of the
deep, but typical crocs only average about fifty meals a year – or just one a week. If humans ate so infrequently – rather than
tucking into three square meals a day plus snacks – our food bills would definitely
be much cheaper, it’d also be much easier to feed everybody around the world, and we’d
only need a tiny fraction of the land we use now for agriculture. Theoretically, nobody would ever have to go
hungry. Of course, you still could eat three meals
a day, if you wanted to. But, with the much slower metabolism of a
cold-blooded creature, the calories wouldn’t have anywhere to go, and the added food would
translate into fat. In lots of warm-blooded animals, fat is pretty
important and essential – keeping mammals like seals and whales warm in freezing oceans,
for example. But it could prove deadly very quickly were
we cold-blooded, causing us to overheat and die. Luckily, as a cold-blooded being, you should
never feel hungry enough for this to ever actually happen… but over-indulgence would
definitely be off the menu. Assuming that you don’t eat too much, though,
it’d actually be harder to get sick as a cold-blooded animal. The constant heat of an endothermic homeotherm
(as we currently are) provides a perfect incubator for germs, which is why it’s so easy for
us to get sick from just being near other sick people. But, if we were cold-blooded, our bodies wouldn’t
be able to cultivate these germs as easily, staving off potential infections. There is a deadly caveat, though, because
our new-found cold-bloodedness wouldn’t make it impossible to get sick; and if you
did fall ill, the consequences could be dire. You may not spread your disease, but if you
got just a little too cold – say your heating breaks, or the wind picks up when you’re
waiting for a bus – your lowered body temperature could damage your immune system. If an ectotherm is too cold for too long,
their body could stop functioning, leaving them wholly unable to fight off disease and
infection. As warm-blooded creatures, we can live anywhere
with relative ease, usually by just adding or removing layers of clothing. We can even survive the likes of Antarctica
with the right equipment. But, if we were cold-blooded, the state of
our environment becomes a matter of life or death every single day. Where most warm-blooded creatures maintain
a body temperature of around 37 degrees Celsius, a cold-blooded creature is exactly the same
temperature as its environment. So, if humans were suddenly cold-blooded,
we’d be much better off living in jungles and deserts, along the equator and in the
tropics, never straying too far north or south. If we did branch out to a colder region we’d
need to build complex habitats, designed to maintain a constant, reliable, 24/7 temperature. Going outside for just a couple of minutes
could result in death, so human settlements would have to be high-tech places – with
our fundamental need for tolerable temperatures at their heart. Strangely, though travelling to places like
Canada, Russia or Scandinavia would be a lot harder, travelling into space might actually
be easier if we were a species of advanced ectotherms. This is because it’d theoretically be easier
to go into torpor if we were ectothermic, which is a state of total inactivity some
animals can enter by slowing their metabolism to a stop. Putting humans into deep sleep is a staple
sci-fi idea, but it’d be all the easier if we could just do this naturally, without
the need for complex technologies that we haven’t yet invented. Send some deep space astronauts on a shuttle
to Mars and (if they’re cold-blooded) they could nap through the whole journey, meaning
they needn’t take as much food and water with them, and they needn’t deal with the
loneliness. Though, of course, actually living on Mars
would be just as tricky for any ectotherm, since the Red Planet’s average surface temperature
is minus-60 degrees Celsius. There’s one final thing that’s pretty
important, though: brain function. The human brain uses about 20% of our current
energy levels, which is 20% of our daily caloric intake. Clearly, if we only ate one meal a week, our
human brains wouldn’t receive the same power to reach the same levels… It’s why the world isn’t really run by
a race of advanced lizard people. If there actually were lizard people, they’d
be evolutionarily obliged to spend most of their days sunbathing just to get their brains
and bodies to work – and they’d have to stay stuck on the equator, to even begin to
match the potential of a warm-blooded rival. So, even with space travel, the problems would
again outweigh the plus points. Yes, we might stand more of a chance of actually
getting to other planets, but would a cold-blooded crew be clever enough to work out what to
do next? Probably not. With this in mind, if humans had always been
cold-blooded, evolution wouldn’t have happened in even remotely the same way. We certainly wouldn’t be such a social species,
and our hunter/gatherer instincts wouldn’t have developed as they did. Instead, we’d all have sat around waiting
for our next meal to arrive, expending all of our limited energy on trying to catch it
in one strike – just like real-world reptiles do. It’s why you see crocodiles floating ominously
in the water for hours on end, biding their time, for absolute efficiency. Even if we did have some intelligence, we
wouldn’t have needed to co-operate to do things like build, farm, and generally invent. The only time we’d ever really need to have
met other people would’ve been for procreation. And, even then, reptiles and fish aren’t
exactly known for their parental instincts, instead tending to leave their offspring to
fend for themselves, or else ditch them before they’ve even hatched. And, as well as all of that, we probably wouldn’t
even be bipedal. Instead, we’d crawl around, spreading our
bodies to expose as much of our skin to the sun as possible, in order to increase our
brain function. True, nobody would ever go hungry because
of our extremely low metabolisms. But, we also probably wouldn’t care if anybody
went hungry in the first place, because an ectothermic race of humans would essentially
all be lazy, antisocial lizards. And, that’s what would happen if humans
were cold-blooded creatures. What do you think? Is there anything we missed? Let us know in the comments, check out these
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