Did Every Language Evolve from Just One?

Also, does John have a favorite extinct language?

Which language would you resurrect?

Max Schmalzl asks whether there is evidence that all languages emerged from one, or whether there were separate emergences of human language, with resemblances between at least some unrelated families due to contact over time.

So, I take it that he means: Is it possible that, say, human language emerged independently in China, long after it had first emerged independently in Africa, and that the only reason someone might today see Swahili and Mandarin as variations on a general human language pattern is that there have been contacts between languages for endless millennia (such as maybe some influences across the Silk Road reaching from Africa to China)?