How Do We Know These Are Different Species?

Although outward appearances vary widely, all modern humans have strikingly similar skulls. They have defining features that differ from those in early human skulls.

The same holds true for early human skulls. Features such as the shape and size of the braincase, face, and teeth distinguish each fossil species.

Neanderthal silhouetteImage of modern human silhouette with bones

Neanderthal                                                Modern human
Large brow ridge                                           Small brow ridge
Low forehead                                                High forehead
Middle part of face juts out                           Middle part of face is beneath forehead