1.24.2020 2:00 PM

They dead.

5 theories on why Neanderthals went extinct

There's a reason we're the only humans left on Earth.

Some 300,000 years ago, nine human species lived on Earth. Today, Homo sapiens are the only members of our genus left. What happened to the rest of the humans is a paleoanthropological cold case.

Of particular interest is the disappearance of our closest relatives — the Homo neanderthalensis, or Neanderthals, who went extinct 40,000 years ago.

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The first Neanderthal fossil was found in Belgium in 1829.

But it wasn't until 1858 that scientists realized they were dealing with a different type of human.

It all had to do with a skull.