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Darwin-L Message Log 5:39 (January 1994)

Academic Discussion on the History and Theory of the Historical Sciences

This is one message from the Archives of Darwin-L (1993–1997), a professional discussion group on the history and theory of the historical sciences.

Note: Additional publications on evolution and the historical sciences by the Darwin-L list owner are available on SSRN.


<5:39>From hantuo@utu.fi  Sat Jan  8 18:42:10 1994

To: Darwin-L@ukanaix.cc.ukans.edu
From: hantuo@utu.fi (Hanna Tuomisto)
Subject: Re: Aquatic apes revisited
Date: 	Sun, 9 Jan 1994 02:45:11 +0200

Finn Rasmussen wrote:

>Why are some hypotheses preferred for others by the scientific
>community? The answer is (or ought to be) quite simple:
>because they are more parsimonious, i.e. they need the fewest
>possible assumptions to explain the observations at hand.

That's exactly what John Langdon kept telling me during our lengthy
discussions about human evolution. And I kept telling him exactly the same
thing. Which means that we agree on the principle how the controversy
should be resolved, and yet we keep getting at diagonally opposing
conclusions.

>   It occurs to me after following the aquatic ape controversy
>in this list  that the "terrestrial ape theory" is vastly more
>parsimonious than its aquatic competitor, as judged from the
>arguments that has appeared in the list

Elaine Morgan wrote a very recommendable book about this in 1990 called The
Scars of Evolution: What Our Bodies Tell Us about Human Origins. I'll quote
from page 5 of the Penguin Books edition:

"Four of the most outstanding mysteries about humans are: (1) why do they
walk on two legs? (2) why have they lost their fur? (3) why have they
developed such large brains? (4) why did they learn to speak?
The orthodox answers to these questions are: (1) 'We do not yet know'; (2)
'We do not yet know'; (3) 'We do not yet know', and (4) 'We do not yet
know'. The list of questions could be considerably lengthened without
affecting the monotony of the answers."

Ask a question, and the generally accepted theory does not give you any
answer. I know there are plenty of suggestions for individual traits, but
none of these have become generally accepted, and most of them won't fit
very well together because they require noncompatible assumptions. There
seem to be only two things that everybody agrees upon: 1) humans and chimps
share a common ancestor, and 2) humans became different from the chimps
because they moved out to the savanna while the chimps stayed in the
forest. But it has been incredibly difficult to figure out where all our
apomorphies came from, because ecologically they make little sense in the
savanna environment. Therefore most hypothesis are based on behavioral
patterns, such as foraging, family structures or sexual selection. Needless
to say, such characteristics don't fossilize, so the hypothesis are based
on no hard evidence. That's why they can be so many and so diverse.

But if we accept one basic assumption, namely that the ancestors moved to
the seashore instead of the savanna, it all starts to make sense. We have
plenty of analogous cases for several traits among aquatic or semiaquatic
animals, and even such traits that cannot boast with convergent evolution
can often be explained in a physiologically and anatomically logical way.
This applies, for example, to the four questions presented above.

On balance we have the terrestrial theory with lots of ad hoc assumptions
but few answers on the one side, and the aquatic theory with one ad hoc
assumption and lots of answers on the other.
Which is more parsimonious?

>I have not read Morgan's book, but
>one gets the impression from the debate here that Morgan is to
>some extent politically flavoured.

Her first book (The Descent of Woman, 1972) attacked the male chauvinism
that prevailed in paleoanthropology in the sixties. The aquatic ape was
presented there mainly as a polemic alternative to the prevailing doctrine.
But her two latest books (The Aquatic Ape, 1982, and Scars) concentrate on
scientific evaluation of the different theories about human evolution on
the basis of the available evidence.

But in a way you are right, I suspect that many people reject AAT mainly
because they are afraid that supporting it would label them as supporters
of feminism. Just like in the discussion around heroes in science a few
days ago it appeared that people tend to judge theories on the basis of the
person who proposes them in a "take it or leave it" fashion. Either you
believe everything, or you believe nothing. Evaluation of ideas just as
hypothesis with no personal label on them is really difficult, although
that should ideally be the way science takes.

>Wouldn't it
>clarify the status of the ideas to simply tabulate the pro's
>and cons?

It certainly would. The problem is that the proponents of the terrestrial
theory refuse to present their evidence. As far as I know, there is exactly
one book where such an evaluation has been attempted (apart from Morgan's
books, but those of course do not count since she reached the "wrong"
conclusion). The book is called The Aquatic Ape: Fact or Fiction, edited by
Roede et al., published in 1991 by Souvenir Press. Frankly, I was rather
disappointed at the quality of the chapters that the terrestrial side
presented there.

Jere Lipps asked:

>How about all ape fossils are terrestrial?  Or is that too late in their
>phylogeny to satisfy you?

It's hominid fossils that matter here. Most of the fossils were found in
the savanna, but not formed there. Savanna is a non-depositing environment
that does not preserve fossils well. Hence, fossils are formed mainly in
rivers, lakes, seashores, caves and in connection with volcanic eruptions.
It is often claimed that the aquatic theory lacks any support from fossil
evidence, or even that the fossils show that the early hominids were
terrestrial, not aquatic. To me, this seems a rather strange interpretation
of the fact that the most important hominid fossils have been found among
fish bones and turtle shells.

Hanna Tuomisto

PS. Sorry for the long reply, John. I know you have seen much of this before.

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