Practice English Speaking&Listening with: CRISPR and the Future of Human Evolution

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[MUSIC]

Is there something youd 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 ones played this game before.

[music]

Mutation and selection.

These two principles have molded basically all life on Earth, from pond scum to platypuses.

Evolutions rule book says changes to lifes 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 byya know, the universe.

But humans are rewriting these rules in incredible ways, putting us in charge of our evolution.

For starters, weve massively changed our environment so its much harder to die.

Theres almost no chance a predator or another human will kill you today, science can repair

our bodies or make us invincible to enemies we cant see.

And more people die today from having too much to eat than too little.

For thousands of years weve 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 evolutions

gas pedal.

DNAs 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 lifes 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

doesnt 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.

Thats where CRISPR gets its name, its a bacterias 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 dont 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 arent technically that different,

but theyre 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 babys 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

planets 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.

Whats 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.

Its 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 were doing about the story of our species: In other

videos, we talked about where we came from, how were all connected, and how were

all related.

If you havent already, check out the rest of the series.

And be sure to subscribe so you dont miss any of our videos.

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