Re: Tools & Canine Reduction

Matthew Hill (mhill@WATARTS.UWATERLOO.CA)
Wed, 22 Feb 1995 12:54:47 -0500

On Tue, 21 Feb 1995, SS51000 wrote:

> J. M. Ottevanger asks about the connection between manipulative
> intelligence and canine reduction. The hypothesis is that selective
> pressure for large canines relaxed because their main function,
> fighting, had been taken over by hand-held weapons. C. Loring Brace
> argues rather convincingly that under relaxed selective pressure,
> structural reduction is to be expected because the "probable mutation
> effect" is to inhibit rather than enhance a growth process. (I prefer a
I haven't at the moment time to check the source (Washburn?), but I am
impressed(sufficiently so to present it to intro students) with the idea that
interlocking canines are disadvangeous because they interfere with
efficient molar grinding. Given the obvious stress on molars in
mastication amongst australopiths, it would seem that conflicting
selective pressures would develop.
If heavy grinding action resulted in accelerated canine wear (and does
this not occur in A. afarensis?) the result would likely be increased
levels of infection, breakage, etc. raising selective pressures for
reduced canines.

Is anybody else familiar with this argument or have I expanded somebody's
chance remark into a causal mechanism?