Geek post incoming!
I love reading around human evolution; especially the evolution of language; particularly syntax and the neurological wiring of grammar. A lot of this is based from endocasts of skulls from archaic hominids, primates and anatomically modern humans, and then using the endocasts to search for signs of language development (e.g. imprints on the side of the skull suggesting Broca’s area – the speech production part in the brain). The hypoglossal canal (bony ‘tunnel’ in the occipital region) also shows differentiation between apes and both modern and archaic humans – the earliest being that of Australopithecus afracanus.
One of the most interesting hypotheses I read was that the rise of language was concomitant with the development of cognitive consciousness. This means that once we, as a species, (ancestrally speaking, although language has been coincided with the ‘Great Leap Forward” whereby technological advancements between 2.5 million years ago and 250,000 years ago was incredibly slow, then increased rapidly since thus suggesting language development) developed language, with its relevant syntax and grammatical structure, we also became aware of our mortality. This knowledge of impending doom possibly resulted in the first ‘religions’ and the increase in symbolism observed in archaic cave art.