Waiter, there's an ape in my soup!
Phil Nicholls (firstname.lastname@example.org)
26 Dec 1994 18:19:19 GMT
email@example.com (Pat Dooley)
> Well, they were not very good runners; they were definitely
> bipedal walkers; and it is very difficult to conjure up a
> scenario that gets them to a bipedal state without violating
> the principle of non-disadventageous intermediates. So far,
> the AAH does the best job of getting the ape onto his feet
> before the savannah or jungle predators kill them off.
> Well no. Lucy followed the aquatic phase; almost literally.She
> is in the right location for a species moving away from a
> dried up Sea of Afar. There was another 3.5 million years to
> go before we get to us.
And what is truely interesting about Lucy's anatomy is how
much it resembles that of a bonobo. This morning I was
re-reading Frans de Waal's Peacemaking Among Primates,
specifically the section on bonobos (Pan paniscus, also called
pygmy chimpanzees). He (de Waal) offered some interesting
observations that, if true, would support one of the planks in
Hardy/Morgan's AAH. Bonobos differ from common chimpazees in
a number of interesting ways. They have longer legs and when
they stand upright they do so in a way that is more like us
than common chimpanzees. In captivity, bonobos exhibited
bipedal posture more often than common chimpanzees. As de
Waal describes it, a bonobo standing upright looks an artists
conception of primitive hominids with one notable exception --
the big toe is large and divergent.
What caught my attention was the following:
"Both Kano and the Badrians [two primatologists who study
bonobos in the wild --pn] have heard from local people that bonobos
catch and eat fish. For many years field-workers found only
ape footsteps and holes in the mud of small streams, but no
direct evidence fish catching. On a recent field trip,
however, the Badrians saw two female bonobos walking upright,
in the water. They snatched handfuls of floadting dead
leaves, picking out things to eat. After the apes noticed
them and fled, the investigators themselves tried the
technique. They disturbed many small fishes hiding beneath
fallen leaves. Susman has observed that numerous the bonobo
tracks along stream beds lack knucle prints."
At this point, de Waal discusses Hardy's aquatic ape theory
and points out that the part about hominid bipedalism may
in fact have some merit. Given the recent buzz about A.
ramidus and bipedalism emerging in a forested environment the
following scenerio might be valid.
The common ancestor was a generalized forest-dwelling ape
feeding on fruits primarily but also exploiting various fauna
(insects, small vertebrates). Forging behavior included
stream bed foraging for fish. As the forests begin to shrink
during the late Miocene there is increased competition for
fruits. Proto-hominids may have survived this competition by
focusing on stream forging. This provides a reason to perfect
bipedality, as Hardy and Morgan have suggested.
Following the stream beds some proto-homind groups would have
ventured out onto the savanna. Upright posture reduces the
exposure of the body to solar radiation. Occasional
excursions onto the savanna allow for an expanded resource
base and the opportunity to perfect thermoregulatory systems,
increasing dramatically the concentration of sweat glands and
a reduction in body hair. As heat rejection physiology
improves, early hominids move out onto the savannah and
survive by scavanging kills canid and felid predators.
I am willing to entertain the "wading ape" hypothesis to the
extent that it does provide an adaptive advantage for bipedal
locomotion. I still have to reject the notion of convergence
between hominids and aquatic animals. The bipedalism
connection is not convergence since no aquatic mammals are
bipeds. Wading does not duplicate the selective pressures
encountered by full aquatic mammals and can therefore not
explain loss of body hair or increased subcutaneous fat
deposition. It does not explain sweating because aquatic
mammals do not sweat. When they excrete salt they do so via
the kidney as do all mammals. Sweat is not a salt excretion
because the concentration of salt is hypotonic relative to
intercellular fluids and blood plasma.
I sure this will come as a great surprize to many but I would
like to point out that my reasons for entertaining this
hypothesis are derived from observations of bonobos in
captivity and the wild. These establish a behavioral
connection between bipedalism and stream forging. It is also
possible that since stream forging is not observed in other
apes and may in fact be a behavioral specialization of bonobos.
Philip "Chris" Nicholls Department of Anthropology
Institute for Hydrohominoid Studies SUNY Albany
University of Ediacara firstname.lastname@example.org