The missing link is already explained by wild discontinuities in evolution, which are pretty much a given on the evolutionary chain of any species on earth given for how long life that evolves has been present on the planet. There's records of tribes with click based languages that can arrange very effective and powerful hunting squads using spears an overpower even herds or packs of the most dangerous animals in their regions. Yeah they look wildly different than apes, but imagine what they were doing to the other kinda differently looking apes that didn't understand their clicks but understood "pointy stick good", and that happened for thousands of years.

Whole indigenous languages went exting in the late 20th century in places like Bolivia or Australia and even during the 21st century native languages are going extinct in California. In thousands and thousands of years someone trying to re-walk Darwins path may wonder were is the missing link in evolution between something like Aztec and European remains found in the West Coast, when there's none. Species can evolve in isolation and then obliterate each other leaving a discontinuity or clique within the genus, it happens all the time, and it's puzzling but natural.