Look around and you'll 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 ancestor.

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?

[OPEN] 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 would've 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 mine... only inside Neanderthal skulls.

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

They're... not, 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 movement... just like prehistoric boy bands.

[MUSIC] 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 disappeared-poof- about 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 Neanderthals.

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.

We're a lot more related than you think, and we'll talk about that next time.