the more "professional", the more lunatic... :-D
From: Marc Verhaegen (fa204466_at_skynet.be)
Date: 01/28/05
- Next message: Kaz: "Re: Hominid Inbreeding And The Bottleneck"
- Previous message: Kaz: "Re: 61% of Americans believe what?"
- Messages sorted by: [ date ] [ thread ]
Date: Fri, 28 Jan 2005 23:42:08 +0100
I just read this "critique" of AAT (some comments between [ ] )
http://johnhawks.net/weblog/fossils/
Why anthropologists don't accept the Aquatic Ape Theory - One of the most
common arguments about human evolution on the Internet is whether hominids
ever went through an "aquatic phase" in their evolution. The Aquatic Ape
Theory proposes that such an aquatic phase, during which ancestral hominids
relied on a water habitat, explains much of the distinctive anatomy of
recent humans. Proponents of the Aquatic Ape Theory compare the predictions
of their model with the predictions that they derive for a traditionalist
model, which they termed the "Savanna model". In their view, an aquatic
phase provides a better explanation for many human characteristics that the
savanna model finds difficult to explain. For example, why do humans lack
fur? Most anthropologists believe the lack of fur derives from selection
associated with thermoregulation. In this account, humans are unlike most
primates in using sweating as a significant source of evaporative heat loss.
This system is efficient in humans because it exploits the latent heat of
condensation to carry away much more heat than is possible through
radiation, convection, or shade alone. [unproven - the "system" is probably
less efficient (eg, sodium & water-wasting) than that in other primates] But
sweating would not work on a furry hominid, because evaporation from the fur
does not carry away nearly the amount of heat lost by direct skin transfer.
[unproven] The Aquatic Ape Theory rejects this hypothesis, noting that: the
mechanism of sweating in humans is especially wasteful of water--a rare
commodity in the hot savanna ; other medium-sized mammals in the hot savanna
environment do not use this mechanism of heat loss ; the loss of fur has
required the development of a significantly costly form of insulation for
the human body, is relatively thick layer of subcutaneous fat [nonsense: fat
& fur have nothing to do with each other, eg, some mammals are fat & furred,
some are naked & lean] By this argument, the theory proposes that it
makes more sense that humans developed carelessness and their unique
glandular system of sweating [not so unique, see, eg, sealions on land] in
an environment where water was both plentiful and continuously available.
Several other distinctive human features are treated by this hypothesis.
Bipedalism itself is suggested for its value in wading into moderately deep
bodies of water. [only 1 possibility] If the Aquatics Ape Theory explains
so much, why do the majority of anthropologists not subscribe to it? It is
hard to find a clear answer to this question on the Internet. Responses to
the Aquatic Ape Theory both on Web sites and on Internet news groups tended
to digress into the a number of specific topics that detract from an answer
this question instead of answering it. Consider the following list of
responses: "Hominids leading into the water sources available to them would
have nothing to protect them from crocodiles and other large predators."
[many times less relevant than lions in the savanna] "Paleontologists
have never found fossil evidence of this aquatic ape." [nonsense: do they
think H.erectus flew to Flores??] "There may be gaps in the fossil record,
but it is unlikely that those gaps will be filled by new primates and
entirely different from any known form in their ecology." [what "gaps"??
never heard of Mojokerto, Terra Amata, Dungo V Baia Farta etc.etc.??]
Supporters of the Aquatic Ape Theory can provide answers to each of these
questions. They can talk about the great quantity of littoral resources for
a primate foraging along the seashore. They can talk about the rarity of
crocodiles along the seashore and the failure of other land predators to
pursue their prey into the waves. The can talk about the geological record
of sea level changes, as the reason that geological strata that might
contain these ancestors like inaccessible to paleontologists. [sensible guy]
And they can continue to criticize the "Savanna model" as inadequate to
explain human features-especially soft tissue characteristics. This process
itself displays an element of the disingenuousness, considering that the
fossil evidence increasingly suggests that hominids did not originate on the
savanna at all. In fact all hominid sites earlier than around 3 million
years appear to represent woodland of an open or closed nature. [irrelevant
for AAT: AAT is about Homo] It appears quite evident now that our "descent
from the trees" didn't take us out of the woods. As the present evidence
continues to develop, the Aquatic Ape debate gets farther and farther from
relevance. [yes, his "critique" is becoming more & more devoid of any
realism] But if all these issues are distractions, how can we explain the
reluctance of anthropologists to seriously examine the Aquatic Ape Theory?
Proponents of the theory tend to argue that this is more than blindness on
the part of the paleoanthropological establishment. Instead, they argue,
professional paleoanthropologists are engaged in a more or less deliberate
conspiracy to exert their hegemonic control over the field by a
marginalizing alternative viewpoints. In this, some proponents of the
Aquatic Ape Theory take the same position as creationists, arguing that it
is the dominant culture of science rather than the intrinsic value of
current scientific ideas that excludes them from debate. [??] Like most
other professional [professional!! what an argument!] anthropologists, I am
well aware that there is no active conspiracy under way to preclude strange
ideas from scientific evaluation. In fact I have seen many strange ideas
come down the pike over the years that received far more celebrity than
notoriety. The history of new research in the field will show to any close
observer the value of breaking with scientific norms. This is so much the
case in the study of human evolution that has provoked published complaints
on the part of senior scientists. But despite these grumblings, there is
nothing that anyone can do to prevent the publication of credible research
in the field, and little they can do to prevent the publication of
incredible research. There is much more to be gained for young scientists in
pushing a new or outlandish idea that has serious empirical support than in
mindlessly following the dictates of the aging graybeards. From this I
think we can conclude at least something small, that many anthropological
eyes looking over the predictions of the Aquatic Ape Theory would have found
by now some serious reasons to support it, if there were any. But there is
more than a small reason why the Aquatic Ape Theory is not believed by
anthropologists. The large reason is parsimony. Evaluating the parsimony of
hypotheses is a fundamental aspect of the scientific method. The idea is
that hypotheses differ with respect to the kind of assumptions that the
requires to make. Some hypotheses require a large number of assumptions,
others require fewer assumptions. Some hypotheses require fairly
extraordinary assumptions. One of the characteristics of parsimony is the
ability of a hypothesis to link many different effects with a single cause.
It is under this qualification that the Aquatic Ape Theory appears very
appealing. By positing a single assumption-that as yet undiscovered hominids
lived in a unique aquatic environment-the theory is able to encompass the
evolution of several different characteristics of the human body that
otherwise would not appear to be tightly linked to each other. In other
words, the hypothesis appears to be simple as an explanation for many
different characteristics, requiring only one assumption (and its many
associated effects) instead of a separate evolutionary explanation for every
characteristic. But this appeal ignores another fundamental characteristic
of parsimony: and hypothesis that depends on one explanation is more
parsimonious than a hypothesis that invokes multiple explanations. Consider
the proposed "aquatic phase" of human evolution, which the Aquatic Ape
Theory posits to explain human characteristics that are uncommon in land
mammals. Certainly it makes sense that hominids would develop new anatomies
to adapt to such an alien environment. [alien?? the coast alien??] But once
those hominids returned to land, forsaking their aquatic homeland, the same
features that were adaptive in the water would now be maladaptive on land.
What would prevent those hominids from reverting to the features of their
land-based ancestors, as well as nearly every other medium-sized land
mammal? [the scars of evolution, of course] More than simple phylogenetic
inertia is required to explain this, since the very reasons that the aquatic
ape theory rejects the savanna model would apply to the descendants of the
aquatic apes when they moved to the savanna. [savanna?? what is the man
talking about? he doesn't understand a word of it: after our littoral phase
(Pleistocene), we became sapiens, of course - what else??] This is far from
trivial, since fossil hominids did inhabit open woodland starting by 6
million years ago, and did move to open savanna by 3 million years ago. [??
Even if this were true, it has nothing to with AAT, which is about Homo <2
Ma.] Nor can the theory hide behind the idea of exaptation. One might
propose that the features that were originally adapted in the aquatic
environment found new purposes when the formerly aquatic apes moved onto
land. But each of these features still requires an adaptive explanation for
why it would be maintained. And each of these adaptive explanations would
probably be equally credible as an evolutionary hypothesis for the origin of
the characteristics outside the aquatic environment. [the man has an
unrealistic & unscientific black-white view: he seems to beleive that
there's nothing but savanna or aquatic] In other words, the Aquatic Ape
Theory explains all of these features, but it explains them all twice. [:-D
good argument, man!] Every one of the features encompassed by the theory
still requires a reason for it to be maintained after hominids left the
aquatic environment. Every one of these reasons probably would be sufficient
to explain the evolution of the traits in the absence of the aquatic
environment. This is more than unparsimonious. It leaves the Aquatic Ape
Theory explaining nothing whatsoever about the evolution of the hominids.
This is why professional anthropologists reject the theory, even if they
haven't fully thought through the logic.
:-D
The man should at least inform a bit before producing his irrelevancies.
Who has his email address, so I can send him a bit?
And he should look up in the dictionary "parsimony":
For a scientific discussion of AAT (pro & contra) see
http://allserv.rug.ac.be/~mvaneech/Symposium.html
At some time after the human/chimp split ~6-4 Ma, human ancestors were
seaside omnivores: collecting coconuts, shellfish, turtles & turtle eggs,
bird eggs, crabs, seaweeds etc. explains many human traits (absent in
chimps) much better than dry savanna scenarios do: brain enlargement (but
olfactory bulb reduction), improved breathing control & diving skills,
varied vocality, small mouth & reduction of masticatory musculature,
handiness & tool use, reduction of climbing, reduction of fur, more
subcutaneous fat, very long legs & straight body build, reduction of sense
of smell, late puberty, high needs of water, iodine, sodium &
poly-unsaturated fatty acids etc.
Probably this seaside episode happened late Plio- or early Pleistocene when
early Homo followed the Mediterranean & Indian Ocean coasts: Homo fossils or
tools ~1.8 Ma have "suddenly" been found in Israel, Algeria, Iran, Kenya,
Georgia, Java... In spite of sea level changes (Ice Ages), Homo (but not
australopith) remains have frequently been found amid shells, corals,
barnacles etc., throughout the Pleistocene, in coasts all over the Old World
(eg, Mojokerto, Terra Amata, Table Bay, Eritrea), even on islands that could
only be reached by sea (Flores 0.8 Ma
http://allserv.rug.ac.be/~mvaneech/outthere.htm ).
Marc Verhaegen
http://www.onelist.com/community/AAT
http://allserv.rug.ac.be/~mvaneech/Verhaegen.html
AAT = Homo spread along the coasts & had a littoral diet.
- Next message: Kaz: "Re: Hominid Inbreeding And The Bottleneck"
- Previous message: Kaz: "Re: 61% of Americans believe what?"
- Messages sorted by: [ date ] [ thread ]
Relevant Pages
|
|
