[MUSIC] Is there something you’d change about yourself? Not just your hairstyle, but down at the genetic
level? For the first time in human history, the ability
to build and select genetic traits is within reach. Problem is, no one’s played this game before. [music] Mutation and selection. These two principles have molded basically
all life on Earth, from pond scum to platypuses. Evolution’s rule book says changes to life’s
instructions happen more or less at random, and not because an organism needs something,
while selecting which traits are good enough to be passed on, is decided by… ya know,
the universe. But humans are rewriting these rules in incredible
ways, putting us in charge of our evolution. For starters, we’ve massively changed our
environment so it’s much harder to die. There’s almost no chance a predator or another
human will kill you today, science can repair our bodies or make us invincible to enemies
we can’t see. And more people die today from having too
much to eat than too little. For thousands of years we’ve been deciding
which plant and animal traits are useful, which are passed on, and which are not. Thanks to more and more selection under our
control, human life expectancy has doubled in just a few generations. But this simply lets us steer evolution. Once we discovered the molecule that guides
these traits, we realized we could hit evolution’s gas pedal. DNA’s information is encoded in long chains
of nucleotides, and natural mutations, good or bad, happen very rarely and in random spots. In the mid-20th century scientists realized
they could speed up mutations using radiation or chemicals, but the effect was still up
to chance. And contrary to popular belief never, ever,
ever leads to superpowers. Later, in the 1970s, scientists exchanged
entire chunks of DNA between species, creating microbes that manufacture insulin, plants
resistant to viruses, even mice with human genes. They could control what was being edited,
just not where in the genome this new DNA was inserted. What scientists needed was a tool so precise
it could make a single change in 3 billion DNA bases, and cheap enough that anyone could
use it. In 2012, they got it: CRISPR. It sounds like a breakfast cereal, but CRISPR
has the power to literally reshape humanity, combining unnatural selection with non-random
mutations. Evolution could be in our hands. CRISPR was invented by one of life’s simplest
organisms. Just like you and me, bacteria are constantly
under attack by viruses. We can afford to sacrifice a few cells to
fight an infection, but a single-celled microbe doesn’t have this luxury. If a microbe survives an infection, it saves
some viral DNA in part of its genome filled with clustered regularly-interspaced short
palindromic repeats. That’s where CRISPR gets its name, it’s
a bacteria’s immune system, a memory of past infections, to protect it and its offspring
in the future. Those viral mugshots are copied into pieces
of RNA, and loaded into a special protein called Cas9. If the virus infects again, and CRISPR sees
a match, the Cas9 protein cuts up the viral DNA like a ninja. Scientists realized that CRISPR could do this
in any type of cell, and by reprogramming the target, CRISPR could cut any genetic sequence
down to a single DNA needle in a 3 billion letter haystack. Suddenly we have the power to edit genomes
like a word processor. When cells repair cut DNA, they can glue the
ends back together, often trimming a letter or two out and disrupting the genetic code. Or the cell can use another template to write
in new DNA, letting us splice in new genes with surgical precision. Genes can be switched on or off. Infections like HIV cut out. Our own immune system can even be reprogrammed
to hunt down cancer cells. Thousands of human diseases are caused by
mutations in single genes, and each could be reversed with CRISPR. Even complex traits like height or heart disease,
caused by many genes interacting with the environment in ways we don’t fully understand,
might be within reach. But to repair every cell in a body, human
genetic modification has to be done at the earliest stages of embryonic development,
and those changes will be passed on to future generations. It makes you wonder: if CRISPR is one day
used in embryos to Make People Better, would we also use it to Make Better People? Using CRISPR, if parents wanted, say, a blue-eyed
baby, could they order the necessary change in the OCA2 gene? If they wanted a more muscular baby, could
they edit its myostatin gene? Curing diseases with CRISPR and making designer
babies aren’t technically that different, but they’re miles apart ethically. Beyond curing diseases, CRISPR makes us to
ask tough questions. Who decides what is a better baby? What if only the rich can afford to edit genes? Should parents even be allowed to determine
their baby’s genetic future? Maybe they already do, thanks to birth control
and techniques like in vitro fertilization? Welcome to a new evolutionary balance. On one side: most of nature, with natural
selection and random mutation molding a whole planet’s worth of diverse species. On the other side is us, a single species
with tools that could match or maybe exceed the speed and power of evolution as we know
it. What’s clear is the ability to control nonrandom
mutation and unnatural selection in humans, to control a piece of our evolution, is no
longer a question of if we can. It’s a question of if we will. Stay curious. If you want to know more about CRISPR and
the strange future it might bring, our friend Vanessa from BrainCraft put out a whole documentary
about it called Mutant Menu. Head over to BrainCraft and watch the whole
thing right now. It's super interesting and digs into a lot
of what we talked about today in even more exciting detail. This video is part 4 of a special series we’re
doing about the story of our species: In other videos, we talked about where we came from,
how we’re all connected, and how we’re all related. If you haven’t already, check out the rest
of the series. And be sure to subscribe so you don’t miss
any of our videos.
I am a big proponent of mad science. Bring on the party and make this one crazy f-ed up world! We live on a planet of endless war, brutality, and poverty. Any idea that ethics are involved in anything is laughable. Let's play God!
The technology exists; the practical applications are going to exist no matter how things go, it's just a question of how fast.
Even if one jurisdiction bans human genetic editing completely (and that's probably a bad idea), that's no guarantee that someone else won't make it legal and pour research money into it. The only way to keep everyone's hands off of human genetic engineering would be a univocal, monolithic government that would probably have oppressive power far beyond any purported merit in stopping genetic engineering.
I admit freely that I am very concerned about how this could lead. I'm hoping society is wise enough that we collectively decline to try to remove autistic people from the gene pool, for instance; and there is, of course, always the potential that this will further worsen inequality.
That said, I am also hoping we can navigate this halfway well, so that we can receive the benefits as fully as possible and see what we're collectively capable of becoming.
What is the limit of changes that can happen in an adult human being and what can only work in an embryo?
Does anyone else hate the name of the channel?
I enjoy learning, but whenever I go to this channel I feel like someone is telling me that someone is telling me that it isn't ok to be smart. It's just gross.