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Reply to Elaine Morgan
Phil Nicholls (pn8886@csc.albany.edu)
2 Jan 1995 15:41:22 GMT
In article <420484704wnr@desco.demon.co.uk>
Elaine@desco.demon.co.uk (Elaine Morgan) writes:
> Two fallacies seem to be floating around. First, that
> evidence from comparative anatomy is more pseudo than
> fossil evidence. The two are equally valid and should
> complement one another. The discovery that whales descended
> from land mammals was made purely on anatomic evidence,
> but nobody dismisses it as a Just So Story.
I don't think anyone has claimed that there is anything wrong
with the practice of comparative anatomy. For example, I am
interested in the evolution of the brain and with the
exception of endocranial casts, I work exclusively with
comparative neuroanatomy. The issue I believe is what
conclusions can and cannot be supported on the basis of
comparative anatomy.
Taking the example you give the ancestry of the whale was
determined on the bases of shared homologies with non-aquatic
mammals. In modern evolutionary studies, cladistic analysis
has become very a popular method for determining relationships
using patterns of shared homologies. Such patterns are the
provide a basis for reconstructing phylogenetic
relationships. However, you are not trying to reconstruct a
phylogeny or establish a phylogenetic relationship. You are
reconstructing an ancestor, a protohominid, from
characteristics that you consider to be the result of an
evolutionary convergence. Your premise -- that hair reduction,
sweating, fat distribution and nose shape are aquatic
convergences is also your evidence for an aquatic phase in
hominid evolution and is a classic example of
begging the question.
> Second, that fossil evidence refutes AAT. In fact it is
> Savannah theory that lacks hard evidence. After the ape/
> hominid split and the fossil gap we get first A. ramidus
> from the sediments of a soggy forest. Later Lucy, whose bones
> were eroding from sand among crocodile and turtle eggs
> and crab claws. Virtually all the Rift Valley hominids died
> at the water's edge - lakesides, riversides, flood plains.
> Savannah theory readily explains this by saying none of the
> non-waterside hominids' bones survived. Richard Klein wrote
> in "The Human Career": "The specific site locations reflect
> the occurrence of sedimentary traps with good conditions
> for bone preservation..(but)..both the australopithecines
> and early Homo surely ranged far more widely within tropical
> and subtropical Africa, into areas where fossil sites have not
> been found or may not exist." That is a plausible suggestion,
> impossible to disprove, but it is only a speculation. The hard
> fossil evidence is that of bones sinking into mud and silt.
The vast majority of ALL fossils come from mud and silt. One
of the richest primate fossil sites in Africa is El Fayum,
where hundreds of Oligocene anthropoid fossils have been
recovered from riverine deposits. Were these aquatic
anthropoids? No, they were arboreal. How do we know?
Because their anatomy is consistent with that of arboreal
primates today. Comparative anatomy, used correctly, can
provide meaningful interpretations of the fossil record.
No hominid or ape fossils show any evidence of aquatic
adaptations. None of the living primates that are comfortable
in the water show any evidence of the aquatic convergence.
Now we have fossil hominids -- mostly skulls but occasionally
some postcranial materials as well. Most are found near
sources of water. A ramidus may or may not prove to be a
hominid but A. afarensis definitely was. Was it aquatic?
Well, it may in fact have waded out into shallow water to
forage. However, comparative anatomy tells us only that it was
a terrestrial biped. Some have suggested, based on the
curvature of the toes and fingers, that A. afarensis continued
to climb into trees.
Where would a terrestrial biped most likely have lived in
Africa at this time? In the forest? Forests were shrinking
right about this time. The savannas were expanding. All known
hominids ( A. ramidus excepted for the moment) are found in
mud and silt deposits that border what at the time were
savannas.
Now if A. ramidus proves to be a real hominid then we have
some evidence that bipedalism was perfected in the forest.
Some anthropologists have held this position for some time,
noting that primates that are suspensory feeders like gibbons
are exclusively bipedal when they are on the ground. However,
we know that hominids eventually moved onto the savanna and
this makes it reasonable to conclude that many aspects of
hominid morphology are a result of adaptation to the savanna.
> Laetoli is an exception. Sediments there are airborne, not
> waterborne. But the area of the famous hominid footprints also
> bore footprints made at the same time by an untypically varied
> assemblage of other creatures, suggesting that some at least
> (possibly including the bipeds) were transients fleeing the
> fallout from the successive eruptions of the volcano Sadiman
> which preserved the prints.
What the Laetoli footprints tell us is that a terrestrial
biped made its way over the ash deposits. Possibly A.
afarensis, possibly some different species of hominid (the
lack of curvature in the toes of the feet may indicate it was
not A. afarensis).
> The South African sites are different and more recent,
> from a time when savanna conditions had become established.
> If ramidus and afarensis had been discovered before the
> Taung baby instead of decades later, it is certain that the
> savannah explanation of ape/human divergence would never
> have got off the ground. Only academic inertia keeps it extant.
> It is time they switched off the life support system.
Recent dating techniques are pushing the times back toward
three million years, so they are not significantly more recent
than, say, AL-444 (Johanson's male A. afarensis). The South
African sites are limestone caves and the hominid fossils
found their are most likely deposited by predators.
Had the Hadar materials been discovered before Taung we might
have seen less resistance to the acceptance of
Australopithecines as hominids but I doubt if it would have
changed our conclusions about early hominid paleoecology.
Australopithecines were terrestrial bipeds and the savannah is
the most likely place for them to have been terrestrial
bipeds. Your aquatic detour is an extraordinary claim which
requires extraordinary evidence. Having read _Aquatic Ape_
and _Scars of Evolution_ I find no such evidence presented by
you. I would be happy to present my reasons, point by point,
if you would like.
Academic inertia is a fact. People who have held certain
ideas to be true are unwilling to accept that they may be
wrong. However, I don't think you can blame academic inertia
for the failure of the AAH to make headway in mainstream
anthropology. Whether our ideas about the role of the
savannah are true or not has no bearing on the validity of the
AAH. The Sherlock Holmes maxim you quote in your book does
not apply to science. A theory or hypothesis is supported by
evidence and not by a lack of evidence for competing
hypotheses or theories.
--
Philip "Chris" Nicholls Department of Anthropology
Institute for Hydrohominoid Studies SUNY Albany
University of Ediacara pn8886@cnsunix.albany.edu
"Semper Alouatta"
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