Re: Savanna mammals

On Jan 20, 10:59 pm, Marc Verhaegen <m_verhae...@xxxxxxxxx> wrote:


I'm not interested in just-so opinions, I'm interested in serious arguments.

Aquatic Ape (non)Theory: Comments on a Recent Guest Lecture
by
Cameron M. Smith
PhD, Department of Archaeology
"If you were among the unfortunate crowd who spent a good amount of
time listening to visiting lecturer Elaine Morgan recently,
regarding the 'Aquatic Ape Theory', be advised of the following
points.
1. Aquatic Ape Theory has been scientifically reviewed, and, despite
what was presented at this lecture, it has been found to be severely
wanting. AAT is not a 'credible alternative theory'; it is what is
known as a post-hoc accommodative argument. Strictly speaking AAT does
not really have a coherent body of theory, only a few disassociated
(non)explanations for a few biological characteristics of the genus
Homo. People should be aware that AAT is NOT 'mainstream' or 'a viable
alternative' as claimed at the lecture.

2. AAT is poorly regarded because it is a poor explanatory device. It
is poorly regarded because it has been examined and found to be
invalid. It is not poorly regarded because of some scientific cover-up
or paranoia. It is not poorly regarded because scientists cannot
accept change. Scientific knowledge does change, all the time, and it
has been pointed out that science is the worst place to try to hide
anything because fraud will be exposed through experiment. AAT is
simply a theory that has been evaluated (and ditched) by most serious
anthropologists.

3. The presentation on 14 October is an embarrassment to Simon Fraser
University, and the sponsoring hosts. How this pop/crypto/science
'theory' was given equal billing with real research efforts is beyond
me. The fact that the 'theory' was included in a series of lectures
dealing with darwinian processes (The Institute of Humanities' 'Old
Minds and Bodies in New Worlds: A Darwinian Perspective on Our Past,
Present and Future' lectures) is a travesty, as AAT crumbles when
examined for internal darwinian logic. Unfortunately, having the
speaker lecture on AAT was akin to having SFU sponsor Erich von
Daniken to speak about spaceship depictions in Maya tombs.
Here's a point to consider when evaluating AAT. I did not learn this
point from some academic overlord with an anti-AAT agenda; I learned
it while trying to avoid becoming crocodile food in Africa. When I
spent several months with a team at Lake Turkana, Kenya, investigating
some of the most important early hominid sites in the world, one of
our overriding concerns -- while swimming, bathing, or catching fish
with a net -- was to watch out for crocodiles in the shallows. A croc
can be on you, crush your legs in its jaws, and drag you under to
drown before you have time to screech for help.
The fact that crocodiles co-existed in time and space with early
hominids is a colossal blow to AAT, which does not explain what
advantages early humans would have gained by spending time in
crocodile-populated waters; an environment where they could not make
fires, throw stones or sticks, use other tools, or have any hope
whatever of escaping the most common predator. A troop of early
hominids wading in a lakeshore or swampy forest would best be
described as a crocodile banquet. The cute, feel-good images of babies
swimming freely in a pool, shown in the AAT video, have nothing to do
with the real situation of predator avoidance in Africa. Ask the
Dasenich or Turkana people who live around Lake Turkana: only visiting
maniacs swim in that lake.
There's much else to say, but I have a 650-word limit. Please keep in
mind, the 'savanna hypothesis' has indeed been largely abandoned, but
that does NOT validate AAT a priori. Neither is AAT validated because
of the common sentiment that 'it is someone's opinion, and everyone is
entitled to an opinion'. Opinion is not the same thing as scientific
theory.
The damage of this lecture was to those who came to the lecture
expecting, and possibly believing, that AAT was a viable body of
theory. It is not, and it does not deserve that label."
Cheers,
Cameron M. Smith



Bramble and Lieberman (2004), in a much-discussed review article in Nature,
cite a number of derived Homo features they claim to be adaptations for more
efficient endurance running in arid, open habitats.

http://www.newscientist.com/article/dn12381-duplicate-genes-help-huma...
July 2007
Human beings can run long distances because we carry multiple copies
of a gene
that helps supply our cells with energy, a new study suggests. That
supports
the idea that endurance running gave our human ancestors an
evolutionary edge.

http://www.newscientist.com/article/dn12381-duplicate-genes-help-huma...
"Human beings can run long distances because we carry multiple copies
of a gene
that helps supply our cells with energy, a new study suggests. That
supports
the idea that endurance running gave our human ancestors an
evolutionary edge."

http://tinyurl.com/7u5wo
“ In fact, he walked and ran with better mechanics than we do today.
The mechanics of his femur, femur head, pelvis, and lower back are
superior to those of today. We have had to sacrifice some of that
efficiency of walking and running to give birth to children with
larger brains.”

Leakey (1994:55): “Two indepandent lines of research converged on the
conclusion that early Homo was an efficient runner, the first human
species to be so.”

http://www.mnh.si.edu/anthro/humanorigins/ha/WT15k.html
“The hips were more slender and adapted to walking and running over
long distances.”


http://news.bbc.co.uk/cbbcnews/hi/animals/newsid_1804000/1804830.stm
Man beats horse in 50 mile desert race

http://www.naturalhistorymag.com/master.html?http://www.naturalhistorymag.com/1206/1206_samplings.html
December 2006–January 2007
Running Man Couch potatoes may disagree, but people are fairly well
built to run in the heat. We sweat more per unit of body surface area
than any other animal, and our upright posture exposes less body
surface to the sun than would walking on all fours, and more surface
to the cooling wind. On the hunt, those traits give people a distinct
advantage over most quarry. In fact, Australian Aborigines and various
Native American and African groups have traditionally practiced
“persistence hunting,” chasing antelopes or other game in the midday
heat, often for hours, until the animals overheat and collapse.
During the past twenty years, Louis Liebenberg, an animal tracker and
the owner of CyberTracker Software in Cape Town, South Africa, has
observed the only persistence hunters still left, the !Xo and /Gwi
bushmen of the central Kalahari in Botswana. He reports a success rate
as high as 80 percent—and a meat yield that beats hunting with bow and
arrow, club, or spear. Only hunting with dogs proved superior.
Conditions have to be just right: the days must be long and hot, and
the terrain must slow down the quarry. Furthermore, the hunters must
be terrifically fit—the runs Liebenberg observed lasted as long as six-
and-a-half hours and covered as many as twenty-two miles. And the
hunters’ tracking skills must be exquisite; finding and following the
quarry every time it bolts out of sight or mingles with a herd is no
easy task—teamwork helps. But done right, Liebenberg says, persistence
hunting is so effective that it may have helped select for the
excellent thermoregulatory system, bipedal posture, and long strides
that we all possess. Perhaps sadly, the practice is dying out, though
the physical skill endures in those who shun couches and run for fun.
(Current Anthropology)
——Stéphan Reebs





 However, while some of
these supposedly Œcursorial adaptations¹ appear first in the fossil record
in H. habilis, others appear first in H. erectus, and others still in H.
sapiens, suggesting a much more complex story than proposed by Bramble and
Lieberman.  Their conclusions are reached without systematic comparisons
with other animals (including endurance runners) and with general
comparisons restricted to fossil hominids and Pan.  Since convergent traits
are strong indicators of evolution in similar environments (Bender 1999), a
systematic comparison with a broad range of animals with a variety of
locomotor strategies would have been more informative.
In addition, discussion of possible locomotion styles is restricted to
walking and running, with no consideration at all given to activities such
as wading, swimming or underwater foraging, yet humans are regular waders
and more accomplished swimmers and divers than other primates.  Most of the
list¹s Œadaptations¹ for walking could just as easily be explained by
wading.  One of the frequent Œexplanations¹ in the list is ³stress
reduction², a reference to the vertical posture of humans with the weight
resting on two legs.  But this says nothing about endurance running, with
standing, wading, walking or short distance running all using a similar
posture, and therefore all requiring stress reduction.  Other Œexplanations¹
include ³counter rotation², ³thermoregulation² and ³stabilization², but no
comparative data to corroborate these interpretations are provided.  In
other words, their Œexplanations¹ are ad hoc suppositions, applied to one
example (human ancestors) without any consideration as to whether these
supposed adaptations are seen in other animals, which means their
Œexplanations¹ are statistically invalid (n=1).  Long legs, and possibly
shortened forearms, could be seen as running adaptations, but these are just
as typical of wading and swimming species compared with runners (Hildebrand
1974: 584, Bender 1999).
In a waterside scenario, wading and swimming would be preadaptative to the
humanlike Œvertical¹ locomotion that Bramble and Lieberman (2004) believe to
be a direct adaptation to endurance running.  In our view, frequent
terrestrial locomotion, whether for walking or for (relatively slow)
running, was more recent (Homo sapiens) and could not be derived directly
from an ancestral locomotion in forests, whether on the ground or in the
branches, because in that case a more baboon-like locomotion would be
expected (the Œbaboon paradox¹).
Most of Bramble and Lieberman¹s Œadaptations¹ are not what we would expect
in a cursorial (running) animal.  For example, their list includes ³enlarged
posterior and anterior semicircular canals², but there are no comparisons
with, for instance, giraffes (heads high above the ground), gibbons (fast
and versatile locomotion), kangaroos (cursorial bipeds), or swimming or
diving species.  It is conceivable in fact that the frequent change of
posture seen when diving for seafood (descending and ascending) required a
different labyrinth structure, and that the larger Homo erectus labyrinth
was adapted to terrestrial walking and running as well as to wading,
swimming and diving locomotions.
There is no indication that an ³expanded venous circulation of neurocranium²
had anything to do with thermoregulation, but there is long-standing
evidence of expanded venous networks in diving species (Slijper 1936).
More balanced heads and short snouts are not seen in cursorial species,
whether bi- or quadrupedal, and low shoulders are to be expected in wading
and underwater swimming.
What Bramble and Lieberman refer to as ³narrow body form², ³narrow thorax²
and ³narrow pelvis² is not clear to us: compared to most primates, humans
have a relatively broad thorax and pelvis (laterolaterally), and this was
even more so in the case of australopithecines. In our opinion, the
combination of Œflared¹ iliac blades and long and relatively horizontal
femoral necks as seen in Homo erectus indicates well-developed ad- and
abduction, which is obviously not an adaptation for running, but would not
be unexpected and indeed would be advantageous for a species that had to
regularly wade, tread water, swim or climb.  In Homo sapiens the pelvis
(bi-iliac diameter) did become narrower and the femoral necks shorter and
more vertical, and we agree with Bramble and Lieberman that this could be
related to more frequent terrestrial locomotion.
Plantar arches, enlarged tubera calcanei, close-packed calcaneo-cuboid
joints and short toes are not seen in cursorials, whether bi- or quadruped,
to the contrary: running species are typically unguli- or digiti-, not
plantigrade, and typically have elongated toes.
In conclusion, comparative data suggest that none of the features described
by Bramble and Lieberman (2004) are typical either of savannah dwellers or
frequently running animals, whether slow or fast.  Until the features are
considered in the context of swimming and wading as well as terrestrial
movement, their interpretations should be considered with extreme caution.
As it is, there is no obvious reason why any of the features cited could not
have been of advantage in a littoral environment.  We do not deny that
humans today are adapted to terrestrial locomotion including walking and
moderate running, but in our opinion the peculiar human anatomy is not
directly derivable from a typical primate ancestor who moved from closed to
more open, arid habitats.


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