Re: Mosaic Evolution and Parsimony

Mr J.M. Ottevanger (J.Ottevanger@LIVERPOOL.AC.UK)
Sun, 12 Feb 1995 14:41:37 +0000

> evidence, to have great antiquity in hominid evolution, and cannot at
> this time be chronologically disarticulated. It appears to me
> unparsimonious to assume mosaic evolution until the evidence makes you.
> After all, if the three traits arose as a kind of package, you don't
> need separate explanations; and one explanation for three traits would
> be neater than three explanations.

That may be the case, Bob, but we cannot take three pieces of "knowledge"
(partial as it is) and ignore certain aspects of them, such as their timing.
OK, further finds will doubtless extend our knowledge of the relations
between the events we're discussing, but we do know that they are far from
simultaneous (as you recognise) and in the wrong order for a tool-driven
explanation. However I think we all agree that there may be more than one
contributing factor to each trend.
Looking at the hands of AL288 and the AL333 fossils, I think the evidence is
pretty strong that they are fairly arboreally adapted and lack the expanded
apical tufts and pollical index (not conclusive; own calculations based on
the shortest possible second ray (from the fossils) and an estimated distal
pollical phalanx),and characteristic muscle markings that many suggest are
necessary for dedicated tool manufacture with the hominoid hand (Napier,
What then is your explanation of canine reduction in terms of tool-use, if it's
not closely tied in with social behaviour? (Blame me, not Professor Holloway,
for objecting to its onclusion in your list.) Rob was absolutely correct to ask
for a discussion of the feedback mechanisms etc. that perhaps linked tools,
social factors and others in driving the evolution of the brain and other
character complexes. We won't get anywhere looking for a "magic pressure", as
fictional as an anatomical magic trait. Oversimplification is one problem with
supposed parsimony. Another is the appropriation of the word to disguise
ignorance (as in the ignoring of) evidence that would require a more involved
explanation. Of course it would be nice to have one neat explanation for every-
thing, but we are not mathematicians or theoretical physicists and so this
is not our role, and besides the answers would be much less inteeresting. I know
we want make-do theories whilst waiting for evidence, the thing that most
worries me is that people forget their Nissan-hut nature and cling to them when
said evidence appears. We aren't at the stage where we can define the pressures
that brought us here, to the Net, but we should look out for intricate paths as
well as straight-forward ones because they might be the paths of least
resistance i.e. parsimonious, as I understand it.
Because of all this, and sorry if I bored you, I don't accept the neat
explanation you offer. I do appreciate the final points you make:

(1) all known human societies rely heavily
> on the making and using of tools for their survival, while no other
> known species does so; (2) many species manage social relationships well
> enough to live in societies at least as large as foraging bands without
> need of human-like intelligence, so the social-intelligence hypothesis f
> ails at the outset (and lacks the tremendous parsimony of the technology
> hypothesis);and (3) rudimentary tool-use, more developed than in any
> species save our own, occurs precisely where, according to the
> technology hypothesis, it should: among our nearest living relatives,
> the chimpanzees.

but hold that number 2 only demonstrates that other species (with different
environmental and phylogenetic constraints) have not paralleled our evolution,
which is not the same as saying that they (or a member that initially founded
the trait) would not have benefited from more complex skills: of deception,
of negociation, of cooperation etc. Dunbar suggests that, besides, neocortex
size does correlate with group size, although he may push it a bit far.
Anyway, group size is not the only variable in the social requirements of a
gregarious animal. There were perhaps unique demands made of early hominids,
that complex social arrangements and skills would have been one suitable answer
to (see the recent discussions re the Ik etc.)
This is most stimulating, cheers all,