Why Are We The Only Humans Left?


Look around and youll meet some pretty smart animals, but there’s no species quite

like us.

But that wasn’t always true.

As recently as 50,000 years ago we walked the planet along with at least three other

human species.

Denisovans and real-life Hobbits Homo floresiensis didn’t leave much behind to know them by,

but Neanderthals are a different story.

A richer story.

The first people to hold Neanderthal skulls didn’t know what to make of them, until

Charles Darwin published his theory of evolution.

Like every living thing, modern humans must have descended from an earlier species, and

lots of scientists thought Neanderthals fit the bill: our primitive, slightly dim-witted


Ernst Haeckel even tried to name them Homo stupidus.

Other scientists had different ideas, they rebuilt skeletons to look like cartoon cavemen,

instead insisting Neanderthals were some failed, evolutionary dead end.

So: Where do Neanderthals fit in the human story?

Were they a bunch of cotton-headed ninny-muggins?

Or were they more intelligent and human than we give them credit for?

And if they were smart, why did they disappear after they met us?

Did Neanderthals really disappear?


If you were sharing a subway car with a bunch of humans and a well-groomed Neanderthal,

you might not be able to tell who’s who.

Buuuut that’s New York for you.

But there were some differences: The big brow ridge.

And huge nose.

The weirdly short forearms and shins.

And BIG muscles.

These were all adaptations to life in cold northern climates, while our skinny ancestors

were built for a warmer, runnier existence.

Our bodies are different, but similar enough that when Neanderthals and our species first

met, we wouldve seen something familiar staring back at us.

Neanderthal life carried serious occupational hazards, considering dinner meant going head

to head with wooly mammoths and rhinoceros like some Paleolithic rodeo riders.

Their fossil remains show healed broken bones, even signs that some were blind, meaning Neanderthal

tribes cared for and fed their sick and injured.

They even buried their dead.

We don’t know if that’s because they were spiritual, or religious, but Neanderthals

definitely weren’t violent brutes.

They were caring and social.

By 250,000 years ago, there were brains walking around in Germany as big or bigger than yours

or mineonly inside Neanderthal skulls.

But if big brains were *everything*, blue whales would be our overlords!

Theyrenot, right?

Neanderthals used this tool about 200,000 years ago.

150,000 years later their technology had progressed to this.

Not ex actly Steve Jobs.

It’s clearly not the size of a brain, it’s how you use it.

Our symbolic thinking, social interactions, technological innovation, and dad jokes just

wouldn’t be possible without our brain’s ability to fancy words together make.

You know: intricate phraseology.

Elaborate discourse.

Complex language!

So could Neanderthals talk?

We know that we and Neanderthals share the same version of a gene, FOXP2, that’s essential

for language, but that gene alone isn’t enough to make a caveman Shakespeare.

The shape of Neanderthal brains inside their skulls suggest they had structures important

for speech.

Their throats were shaped to make more than ape sounds.

That’s most of the ingredients for *some* kind of speech and language.

But rich communication is possible even without mouth noises.

Scientists think Neanderthals could have exchanged ideas and told stories by combining simple

sounds, musical tones, and rhythmic movementjust like prehistoric boy bands.


Around 50,000 YA Neanderthals met their very smart cousins: Us.

For five or ten thousand winters and summers, our ranges overlapped, until Neanderthals

suddenly disappearedpoofabout 40,000 years ago.

Were we friends?

Or enemies?

Wherever our nomadic hunting groups clashed for territory, our species had deadlier weapons.

Whereas Neanderthals lived in socially isolated groups, we readily exchanged technology between

tribes, even traded.

When it came to innovation and competition for resources, Neanderthals just couldn’t

catch up.

Or maybe we just gave them an extinction-level case of the flu.

At their peak, Neanderthal populations probably never reached six figures worldwide.

Like gorillas and orangutans today, they lived in small, dispersed pockets--which means more

inbreeding and less genetic diversity.

Maybe Neanderthals were already endangered when we showed up.

Before they disappeared, Neanderthals left us one present.

In 2010, the Neanderthal genome was sequenced from ancient bones.

That genome was compared to modern human genomes.

1 to 4 percent of the genes from ALL living humans outside sub-Saharan Africa came from


People with sub-Saharan ancestry?

No Neanderthal DNA.

This tells us Homo sapiens shared a romantic campfire with Neanderthals and interbred,

probably right after our species left Africa, spreading that Neanderthal DNA as we settled

the rest of the globe.

Thanks to genetic testing, I know I have more Neanderthal DNA than 70% of people, which

to me is proof that Neanderthals were definitely intelligent and awesome.

So 50,000 years ago we walked beside other humans.

We haven’t completely solved the mystery of why they disappeared, except to discover

that they aren’t totally gone.

They live on inside us, the only humans left.

But the 7 and a half billion of us alive today share more than these distant ancestors.

Were a lot more related than you think, and well talk about that next time.

Stay curious.

Thanks to 23andme for sponsoring this episode.

The name ‘23andMecomes from the fact that human DNA is organized into 23 pairs of chromosomes.

23andMe is a personal genetic analysis company created to help people understand their DNA.

You can see which regions around the world your ancestors come from, learn how DNA impacts your health,

your facial features, hair, even your sense of smell, and how you sleep.

You just have to provide a DNA sample by spitting in a tube.

I learned that I carry a gene that allows me to smell asparagus odor in my pee, and that I’m likely to have a longer second toe than big toe.

Which is true. I have really long toes.

But I also learned that one gene I inherited from my Neanderthal ancestors might be a reason I’m taller than most people.

You can learn more about your personal DNA story and support our show by going to 23andMe.com/OKAY

I studied genetics for my PhD, and learning about my DNA was justso fun. Let us know if you give it a try.

See you next week.

This video is part of our

special series about the story of our species: Where we came from, how were

all connected, and where were going.

If you haven’t already, check out part 1 and retrace the mysterious path of our family


And be sure to subscribe so you don’t miss any of our videos.

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