The Amazonian Languages

16 R M W. Dü;on and Alexandra Y. Aikhenva/d
1 Introduction
17
branch or sllbgroup within it - just as one talks of the Indo-Ellropean family and
the Germanic branch or subgroup within it - in preference to Tupí stock and Tupí­
Guaraní family.)
4 THE PUNCTUATED EQUILIBRIUM MODEL
It is generally recognized among historicallinguists that one can only recognize historical
relationships between languages (and reconstruct shared proto-Ianguages)
to a time-depth of 5,000-8,000 yeaes. Given any longer time, individual languages
are Iikely to have changed too much for their onginal genetic connection to be
apparent. Thus, Greenberg's (1987) views about a relationship between all the languages
of South America and most of those of North America are not
unproven but unprovable.
But ir one views the 'family tree' as the basic model of language relationship, one
must presume that there probably was a family tree joining togethei family trees.
That is, that many of the language famílies (and isolates) of the Americas presumare
geneticalIy related, only one would need a time machine to discover exactly
how. In tbis view, Greenberg's scheme is a perfectly possible one. But there are many
altemative scenarios that are equally plausible, and there is no way of deciding
between them.
We believe that this is a mistaken view. The family-tree model is appropriate for
certain kinds of language development but not for all of them. Humankind is
believed to have had language ror at least 100,000 years (many people would opt for
a longer time-span). Consider the Indo-European family, which has ayer lOO
modem languages and for which a time-depth of about 6,000 years is posited. There
are about 17 periods of 6,000 years in 100,000 years. If one language spawns 102
descendants in 6,000 years, then over 100,000 years it should give rise to
2
10 >