Why would language evolve when the sharing of information doesn’t obviously serve the organism and no trait has evolved for purely altruistic reasons?
A theory by Roger Dunbar proposes that it may have replaced grooming behaviour as a more efficient means of interacting with other group members. This doesn’t explain the content rich nature of language. A theory proposed by the anthropologist Robins Burling in 1986 posits that men receive social status for their public speaking ability which cashes out as reproductive success with male orators preferentially selected. This theory needs to be updated to explain why females also talk given if evolution would supposedly only select for those women better at discerning language, not their capacity to speak it. Male humans invest in children over the long term more than any other primate which results in a mutuality of sexual selection explaining language development in both sexes (unlike the singing seen in only male whales or birds).
The question as to why language is information dense still begs an answer, and this could be rationalised by considering what would be preferentially advertised by big brained humans; intelligence. Data laden language is a good indicator of intelligence and allows for an insight into a mate’s mind, a possibility otherwise unknown in the animal kingdom.