The book The Language Puzzle delves into this a bit - even our closest genetic primate cousins appear to lack the physical adaptations in both brain and voice box/mouth to develop verbal language and written language is a step farther, other species show some signs like cetaceans and elephants. There’s a bit of speculation in there that advanced hand tools and language may have been coincident (from archaeological evidence with close time stamps) and that still took a very long time.