What if the first language was a sort of sign language, and vocalizations were only auxiliary, optional? With time, humans who vocalized had a better chance to be understood, and their vocal tract evolved. Humans instinctively gesture to this day when speaking.
This has been hypothesized, but the fact that there aren’t many or any purely sign languages still around and other primates don’t show signs of using signs makes that seem like a reach, IMO
other primates don't show signs of using vocal language either, yet humans have it
>there aren’t many or any purely sign languages still around
we're the only species of modern humans who survived, maybe Neanderthals/Denisovans etc. used sign language, who knows
maybe the fact that we started using vocal language made us much more superior evolutionarily speaking, making other similar species without developed vocal tracts extinct (by our warfare/assimilation)
deaf/mute people around the world have always historically come up with ways to talk using signs (different unrelated systems), i.e. we still have the means to do it, but it's unnecessary when you can produce sounds (freeing your hands to do work)
I would consider this evidence that language predates human vocalizations. We already know deaf children will invent signs and gestures to communicate, and language not dependent on a hyoid bone. Do we have any way of dating the relevant neural structures through genetics?
I think we’d have trouble because we’d have to tie the gene to a specific linguistic cognitive function. My hypothesis is that humans configured themselves into self-replicating group structures I’d call institutions, and language evolved as a way to facilitate that. These institutions exhibit all the thermodynamic properties of life, and they have goal directed behavior independent of individual humans.
FOXP2 was thought to be the genetic basis for language, but this has been overturned[1]. As far as I know there isn't a good candidate for a gene selected for language.