information:highlighting, structural:expansion, stylistic:tone
Language

The hyoid bone supports the tongue and makes possible modulation of the vocal tract to control pitch and volume. A 400 kya H. erectus hyoid bone from Castel di Guido, Italy, is bar-shaped—more similar to that of other Homo than to that of non-human apes and Australopithecus —but is devoid of muscle impressions, has a shield-shaped body, and is implied to have had reduced greater horns, meaning H. erectus lacked a humanlike vocal apparatus and thus anatomical prerequisites for a modern human level of speech. Increasing brain size and cultural complexity in tandem with technological refinement, and the hypothesis that articulate Neanderthals and modern humans may have inherited speech capabilities from the last common ancestor, could possibly indicate that H. erectus used some proto-language and built the basic framework which fully fledged languages would eventually be built around. However, this ancestor may have instead been H. heidelbergensis, as a hyoid bone of a 530 kya H. heidelbergensis specimen from the Spanish Sima de los Huesos Cave is like that of modern humans, and another specimen from the same area shows an auditory capacity sensitive enough to pick up human speech.