Interesting ping.
Archive?
From The Descent of Man:
"The formation of different languages and of distinct species and the proofs that both have developed through a gradual process are clearly the same."
Almost the same: there's nothing like convergence in linguistics. IE, there is no external force driving language change, it's all inherited change.
I don't have the book in front of me (so I'm paraphrasing), but Merritt Ruhlen in The Origin of Language : Tracing the Evolution of the Mother Tongue uses a biological concept, "out-group comparison", in his logic. He says there are [a few] thousand species of mammal, all but six (?) (platypus and various echidnas) give live birth. Did Proto-Mammal lay eggs or have live birth? All biologists agree that Proto-Mammal laid eggs, because, 1) some mammals do, and 2) their closest non-mammal relatives, the reptiles, all do.
He employs this logic to argue that if a word is found in, say, Finnish and Samoyed, but no where else in Finno-Ugric, then, if it's also found in Yukaghir, (and isn't a loanword), it was part of the proto-Finnno-Ugric language, even thought it's not in Hungarian or Mansi, etc.
Ruhlen is arguing for the monogeneisis of language; in another book, On the Origin of Languages: Studies in Linguistic Taxonomy (BTW, much more technical), he gives a list of 20-some words that seem to be widespread throughout the world's languages.
The most famous example is "tik" meaning "finger"; it's the root behind "digit", "decimal", and perhaps "toe"; it's found in Africa, Asia, Europe and the Americas.
I just googled an interesting discussion of this: Babel and the Ancient Single Language of the Human Race" by G. R. Morton, as in Morton's Demon!
Ping to PH, VR and Junior; Check Glenn Morton's home page. All I've seen previously is his "demon" essay.