TL;DR: Analysis of a neanderthal hyoid bone indicated that neanderthals did not posses a series of air sacs, common to apes, that preclude complex vocal speech

TL;DR: Analysis of a neanderthal hyoid bone indicated that neanderthals did not posses a series of air sacs, common to apes, that preclude complex vocal speech, and thus were mechanically capable of producing sounds comparable in complexity to human language.