The average person can
hold their breath underwater for, like, one to two minutes. But every day on an
archipelago in Southeast Asia, the Bajau people dive down
more than 60 meters deep to catch fish, and they
can hold their breath for more than 10 minutes. How? That's better. This ability, it doesn't just
come from years of training. It's thanks to a genetic
change in this population. In other words, it's an example of very recent human evolution that makes a group of
people better adapted to their environment. But what about the rest of
us? Are we still evolving? As humans live longer, die less, and make more and more tools to protect us from the
dangerous world that we live in, does that mean we've
bypassed that great filter of natural selection? What is the future of human evolution? (light orchestral music) Hey smart people, Joe here. The Bajau people sometimes
spend five hours a day holding their breath. I mean,
that's more time underwater than a sea otter. But what's
even cooler is how they do it. So the secret to their
superhuman breath holding is an actual physiological change. Bajau spleens are up to 50%
larger than yours or mine. You know, the spleen is an
under appreciated organ. It acts like an oxygen reservoir
by storing red blood cells, the ones that carry oxygen. So a supersized spleen means more oxygen can get into your
bloodstream between breaths. Other highly adapted diving
mammals like whales and seals, well they have super spleens too. Now, you and me, we can't
just beef up our spleens by diving a lot. That's
not how evolution works. Bajau divers have lived
in a watery environment for thousands of years. Somewhere along the way,
a genetic change happened that gave some people
there bigger spleens. Those people ate more, they survived more, and over many, many generations, that adaptation became more common. This is natural selection. It's a gene becoming more common
in a population over time, because the individuals who
carry that gene are more likely to survive the pressures
of their environment. Since our species showed up, we've spread to every
environment on Earth. Our ancestors faced countless
environmental pressures. Different foods, different climates, and once we settled down in large groups, domesticated plants and animals, and started building civilizations, we've had to face a lot of deadly germs. Because civilization is filthy, y'all. A lot of people died as a
result of those new pressures, but our ancestors survived, often because of new and
improved versions of genes that they carried. Like Himalayan populations
whose lungs can breathe air with 40% less oxygen than
what most of us breathe. Or people in parts of Africa
who are more resistant to the germ that causes Lassa fever. Or how populations who
migrated closer to the poles developed lighter skin, to make the most of less intense
sunlight at high latitudes, you know, since our bodies need
sunlight to make vitamin D. And speaking of vitamin D, let's
talk dairy. Love the stuff. Calcium in milk also aids
in vitamin D production, but most animals can't
digest milk very well after they grow up. Losers. Luckily, for some of us, a
genetic change allowed us to keep our milk drinking ability
switched on throughout our lives. And because milk is a
reliable source of protein and calories, milk drinking
evolved independently in lots of different places. Changes like these, and countless others that helped shape our species, they happened because
of natural selection. Genes becoming more common because they make it easier to survive. But today is different. I mean, humans have
invented so many tools. We've got medicines, sanitation, environmentally-controlled living pods, more food than we literally
know what to do with. I mean, name the last time
you thought you might be eaten by a tiger on your way
to get lunch, right? People just don't die
as much as they used to. Human life expectancy
has more than doubled over the past 200 or so years. And now that almost everyone
is surviving past the age where they can make babies,
does that mean natural selection doesn't apply to us anymore? Is this the post-Darwin age of humanity? Have we entered the hyper
technological trans-human utopia? Have we stopped evolving? No. Because natural
selection isn't the only way evolution happens, folks. Some genetic changes just
become common by random chance. Let me show you what I mean. This jar is full of M&Ms. Every bag of M&Ms has
this population makeup. But this population of M&Ms
has a very different makeup from the original population, and so will the future population. And that happened because
of a chance event, when I grabbed a random handful. Delicious. I could do that again and again and I'd get different results each time. This can happen to genes too. When random events
decide what genes survive and become more common,
not the environment, that's not natural selection,
it's genetic drift. Let's say a bunch of highly
advanced lifeforms live here. Until a meteor hits.
Thanks to random chance, these ones survive, and over time, the population looks a lot different. Or maybe through a series
of unfortunate events, a few of them end up on this island. What this new population looks like will depend on the
individuals that founded it. This kind of thing
happens with humans too. If you're from European
ancestry, there's a 90% chance, or more, you got wet, sticky earwax. If you're Native American
or from East Asia, you've got about a 90% chance
of having dry, flaky earwax. This difference is caused
by two different versions of a single gene. But the
type of earwax you have doesn't exactly give you
a survival advantage, so which version became more common where is probably just the result
of which gene version was carried by the first humans
to migrate to those regions. Catch my drift? Genetic drift. But the chance effects of
genetic drift are more likely to be significant in small,
isolated populations. And humans are not that.
I mean, we move around, we share culture, and as we move around and mix more than ever,
genes are mixing too. So that's decreased
the genetic differences between human populations overall. And when rare versions of genes do arise, it's more likely that they'll
get diluted out by the mixing. Humans living longer or dying less thanks to our awesome inventions may reduce the effect
of natural selection. Humans moving around, multiplying, and mixing a lot may reduce
the effect of genetic drift. That means really wild new
adaptations like the Bajau's super spleens are probably
going to be less common in the future. When you put
this all together, well, a lot of people have claimed
that as Darwin's ideas lose their grip on us,
and as humans move around and mix ourselves up, we're
going to start looking more and more alike. But that's
not how this stuff works. Even things like skin color or eye color, they involve a symphony of
dozens of genes all interacting in a ton of combinations. I mean, just consider the
variation in physical appearance we already see today in
people with mixed ancestry. People will always be plenty different. There is one more process,
though, that can influence our evolution apart
from natural selection, and it has to do with how babies happen. Ask your parents. Genes don't just randomly find each other. Individuals have a choice
in who they mate with. If you're attracted to the largest, fanciest antlers in a herd, that will lead to fancier antlered babies, even if fancy antler genes
don't necessarily make you better suited to your environment. This is an example of sexual selection, where the genes that survive
are tied to who picks who to do the mating thing. How sexual selection
will impact the future of human evolution, that's up for debate. Let's say the things
we're attracted to today are tied to intelligence,
and many scientists think at least some are. That
might mean more future humans that have traits tied to
intelligence, like bigger brains, or a genetic predisposition
to watch this YouTube channel. Again, this isn't genes
that help us survive a germ or our environment, it's
genes that may just make us more sexy. Now, this last part
may feel a little bit icky depending on how exactly
you feel about things, but thanks to our tools, the
future of human evolution may be, in part, something
that we can control, or at least try to. Our species
already relies on machines to survive and thrive, and
we're only gonna continue to rely more on those
machines in the future. Taking more and more power out of the hands of natural
selection along the way. And we will increasingly
not just depend on machines for help, but one day
we're gonna be physically or neurally integrated with them. And frankly, no one knows
what that will do to our genes or which ones become more or less common. With genetic engineering,
we now have the ability to insert custom genetic
sequences into living things, even ourselves, perhaps even
pick and choose the genes that we want our offspring to have. This is a form of evolution that really no other species can do. How big of an influence
these future forces have on our species is also up to us, but it will almost
certainly have some effect. Evolution is just change. And that's a process that never stops, for our species or any other. Natural selection happens
to be just one way that evolution happens,
but there are many others. So even if our big brains have
made it so natural selection doesn't determine our future
as much as it used to, change is a constant. You know, it's pretty interesting to think that we may be the only
species on Earth with the power to determine at least a little bit of what our future change looks like, and that is a power that comes
with great responsibility. And also hopefully comes
with a cold glass of milk. And an Oreo. Stay curious. Hey what's up guys. I'm down here in Florida
making our next episode. But before you go, I wanna
tell you something that's gonna make the history buffs
out there pretty excited. PBS has just launched a brand new, history focused YouTube channel.
It's called PBS Origins. It's gonna be home to a
bunch of great new shows, but right now, you can go
check out Historian's Take, which is a look at history
through the lens of pop-culture, What old cultures can
teach us about our own, and our future. You're gonna
love it, there's a link down in the description where
you can go check them out, and make sure and tell
them that I sent you. All right, we'll see
you in the next video. And as always, a huge
thank you to everyone who supports the show on
Patreon. We could not do this without your support. If
you would like to find out how you can support the
show and the videos we make, find out what we're
doing behind the scenes, things like that, and
find out about new videos before anyone else, click the
link down in the description. I'll see you in the next video. - [Cameraman] Rolling, and action. - Nice. Bring your cookies. - [Phone] Went wrong, please try again. - Who's talking to you? Okay, we got one shot at that.
