Tools and Brain Expansion

Thu, 23 Feb 1995 13:33:08 CST

J.Langdon writes,

>In tool, social, and foraging models we face the problem of why other species d
>not have big brains. After all, chimps make and use tools, have complex
>societies, and face similar foraging problems. Perhaps there is a threshold
>effect -- once brains reach a certain size, positive feedback takes over and
>increase proceeds exponentially. tion for
Note, though, that tool use and tool making is extremely rudimentary,
which, in conjunction with the small brains of chimps, gives technology
precisely the presumptive temporal priority required for it to have been
causal. Therefore I think of a threshold not of brain size, but of tool
dependency: at some point our ancestors became dependent enough on tool
use that bipedalism and canine reduction--and brain expansion and
symbolization--all were subject to growing selective pressure. I think
it of utmost importance that only the Darwinian theory, which puts tools
in the role of prime mover, allows explanation of all these hominid
trends at once. From my perspective, any attempt to explain some one
of the features suffers a considerable handicap in terms of parsimony.
To compete with Darwin, you need to have a very strong argument that
he was mistaken, or come up with a more compelling explanation of
hominid features in general--especially the bipedalism/canine reduction
combination, but preferably also language and brain expansion. It is
amazing that the rather short-lived rotary-mastication hypothesis, about
which I too am in search of references (a major one being Jungers in
*Current Anthropology* of 1978), which is far less relevant than tools
to *any* of the other hominid features, seems to be the most serious
challenge to Darwin's theory in the 124 years since it was presented.
But then he was Darwin, wasn't he? --Bob Graber