How do we know that Neanderthal skeletons are Neanderthal skeletons?

[Anomalocaris]

Neanderthals were humans, just an earlier less evolved version, and usually the shape of the skull is what differentiates it from modern human remains.

to say neanderthal are less evolved version of humans betray both a misunderstanding of the traits that distinguish neanderthal, and more profoundly a fundamental misunderstanding of what “evolved” means in the context of evolution.