My ignorance of anthropology is definitely showing here, but how can an anthropologist make assertations such as "'The Homo erectus brain did not devote a lot of space to the part of the brain that controls language and speech,' said John Shea, professor of palaeoanthropology at Stony Brook University in New York."? Is it just from skull sizes and shape? Maybe there is far less diversity across skull size and shape in homo sapiens sapiens than I assumed (at least within the brain casing). I'm genuinely curious as to how we can know so much about these species.

Following a link below, I noticed that the genome of homo neanderthalensis (or homo sapiens neanderthalensis) had been sequenced. I imagine that this would allow such knowledge of brain structure.