THERE'S NO SUCH THING AS SPECIES:

It's been over 150 years since the bones first emerged from the Neander Valley--a time during which we've learned a vast amount about human evolution. Today, scientists can even scan the genomes of Neanderthals who died 50,000 years ago. And yet the debate still rages. It's a debate that extends beyond Neanderthals, forcing us to ask what it means to be a species at all.

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