Monogenesis and "simple Darwinian grounds"

[Johanna Nichols]

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This has nothing to do with selection, but note that estimates of the size
of the earliest modern human population (ca. 100,000 years ago) range from
a few tens of thousands to a million or more.  The range within which
modern humans evolved, and within which homo erectus evolved, and so on was
comparable in dimensions and shape to New Guinea, and the ecological
context was riverine and lacustrine tropical.  Under comparable ecological
conditions, modern languages of the least complex societies show tremendous
diversity of language families and languages, as well as small
speech-community sizes for languages (a few hundred individuals per
language in many cases).  There would have been room for a hundred or so
languages and a dozen or so distinct language families in the early human
range.  It's hard to imagine that a species could have been viable if its
entire population was comparable to the modal number of speakers per
language in New Guinea and Australia.
 
This makes it hard for me to believe that there was ever just one language.
There might well be a secondary kind of monogenesis in that all but one
line has gone extinct, not for reasons having to do with selection but
accidentally, by ordinary drift (just as, over enough time in a smallish
population, sooner or later all but one of the last names daughter out and
everybody has the same last name, though that doesn't mean they had only
one ancestor).  Unless dialect differentiation and sound change happened at
very different rates or in very different ways or not at all in the early
stages of language development (which I doubt profoundly, since as I
understand it even bird species that learn their songs have song dialects,
which indicates that differentiation with learned transmission isn't unique
to language), I think language as we know it evolved very gradually from
something more primitive and the entire evolution was as a number of
dialects or languages or indeed even language families.
 
If it weren't for the population size and range factors, I'd vote for
monogenesis.
 
Johanna Nichols