Darwin and language

[Sean Brady]

----------------------------Original message----------------------------
 
Some evolutionary ideas are being discussed in a misinformed fashion.  I
take it that "Darwinian" means something like "due to biological natural
selection on indivduals" (I missed the first message). If so, a few things
need to be cleared up.
 
          The scenario described by Janda:
 
   "That is, even as-
 suming that, due to selection, some mutation which provided the prerequisites
for language came to characterize all living humans at some point, it does
 not follow that there was only one occasion on which sound/meaning associa-
 tions were arrived at and then passed on to succeeding generations.  Rather,
 a language-facilitating mutation could have been selected for but then not
 immediately acted on, as it were (and this does not strike me as unlikely)."
 
is quite reasonable, contrary to the counterargument presented.  This
process, whereby a character that evolved for other functions, or for no
function at all, but which has been co-opted for a new use, is called
exaptation.  Many biological features are thought to have evolved in this
way, perhaps including such dramatic ones as flight in birds.
 
        Also, the process described by DeLancey:
 
  " But I had in mind a different Darwinian argument....  Once one
population has developed an advantageous trait, it will then out-reproduce
competing populations which lack that trait, and eventually replace them.
Once one population has developed language, it's not likely that anyone
else will get the chance.  I'm no archeologist, but I understand that
the archeological record suggests an explosively fast expansion of
modern humans (at the expense of Neanderthals).  The obvious inference
is that a single population developed language, giving it a selectional
advantage which allowed it to overspread the world very quickly"
 
is usually not thought of as "Darwinian" because it defines group
selection, in which populations, and not individuals, are the unit of
selection.  Although group selection has been out of favor for the past few
decades, it is enjoying a comeback lately, and seems a perfectly plausible
mechanism for evolution in organisms such as humans.  But without adequate
information, we can never assume that any population with an advantageous
trait will ALWAYS drive all other population to extinction; there are
countless counterexamples to this assertion in the biological literature.
But in this case, the idea certainly has some merit to it.
 
        Finally, and most importantly, nothing in modern evolutionary
theory that I know of has anything to say about whether a trait can evolve
multiple times or not, which is really what we are debating.  Both
scenarios are perfectly plausible.  This is analagous to the Out-of-Africa
vs. multiregionalism debate in anthropology, in which neither side can say
the other is wrong in theory; evolutionary facts are required to test
alternative hypothesis, each of which are very reasonable.  Until we have
similar types of data concerning langauge evolution (admittedly a lot
harder to get!), I do not think that evoluationary theory has much to
contribue to this debate.
 
 
Sean Brady
Center for Population Biology
University of California, Davis
sgbrady at ucdavis.edu
(916) 752-9977