[LordGronk]

There’s no evidence that Homo Sapiens, aside from some interbreeding with other hominids interacted with other hominids who were capable of complex language for that to be possible. And a multiple origin scenario for behaviourally modern humans flies in the face of modern science, archaeology, and palaeontology to such a degree that it would basically require magic.

[arp242]

How so? Early humans moved around and were all over the place, often with no or little contact. I don't see why two groups of humans couldn't have developed (proto)-language independently. There's lots of examples of things independently developing in multiple places.

[pharrington]

I think what zirgs meant is that since at least one group of humans developed a language, it makes sense that different groups of humans could also independently develop language.

[Sprocklem]

One (admittedly speculative) reason to believe that all natural spoken languages have a common ancestor derives from the fact that modern humans seem to rapidly develop new languages in the absence of an existing language, as was seen in the case of Nicaraguan Sign Language. There is no particularly compelling reason to believe that earlier homo sapiens ­– who were otherwise anatomically modern – would be any different before they began migrating out of africa. This is especially true given that all human populations do ultimately have both an apparently-innate capacity for language, and their own languages.

If this is the case, then the first language would have probably rapidly spread between the early populations in africa – if, indeed, there were multiple distinct populations at the time – and new (homo sapiens–originated) languages would have only arisen if the chain of speakers were somehow broken and children raised without access to an existing language.

With that being said, there are some cases where something similar has happened. Most obviously are sign languages, which are believed to have had multiple origins, since it is possible for deaf people to be born among non-signing populations. Something similar in the case of spoken languages is the phenomenon of pidgins evolving into creoles mentions elsewhere in the comments, although they still retain at least some aspect of one of their parent languages. The extent to which the latter count as proto-languages is questionable.

[ffhhttt]

I don’t think that we can conclusively say (or even close to that) that other Hominids were incapable of complex (to an extent) language.

[ycombinete]

That doesn’t seem to make sense. Surely interbreeding with other hominids requires interaction with other hominids?

[LordGronk]

History shows that many humans of the same species can “interact” without friendly communication, or, for that matter, preserving fully functional languages (Just look at the Minoans, Etruscans, Harappans, Rhetics, and the numerous other peoples who spoke something that we can’t read, or can understand but only with great effort)