Shortly after modern humans arrived in Europe, the Neanderthals disappeared. And scientists think we had something to do with it.

Neanderthals, or their direct ancestors, migrated out of Africa and into the Middle East and Europe around 250,000 years ago. Soon they were well adapted to the environment.

Large eyes helped them see in the longer nights and darker winters. Stout bodies helped them retain heat and handle large prey, and provided space for the large liver and kidneys needed for a diet heavy in protein.

Their brains were as big as ours but spent processing power on their greater visual and motor abilities. This may not have allowed them to develop higher communication or conceptual thinking to match ours. Which may have been their downfall.

Modern humans arrived on the scene 45,000 years ago, less physically adapted but more mentally adaptable.

We had cooperative hunting methods superior to the Neanderthals’, allowing us to out-compete them for food and perhaps reducing the large herbivore populations that they depended on.

We also had superior tools and weapons. When there were conflicts between the groups—as there have been among tribes throughout history—our superior technology probably allowed us to prevail.

But we weren’t only fighting. There must have been considerable interbreeding, since we can find 1 to 3 percent of the Neanderthal genome in modern man.

Which means the Neanderthals never completely disappeared. A little bit of them is alive in us today.