Re: Aquatic canines and other holiday musings
Bryce Harrington (bharring@aludra.usc.edu)
18 Dec 1994 18:27:23 -0800
In article <055jkms.4@chiron.wits.ac.za> 055jkms@chiron.wits.ac.za (JEFFREY K McKEE) writes:
>
The
>recent discovery of <Australopithecus ramidus>, IF it proves to be a
>hominid, would seem to be a problem. It is dated to 4.4 Myr, is VERY chimp-
>like, and was found in a forested environment, not by the sea.
Now, I read through the articles announcing this find, but it seemed to
me that there were just not enough bones to make any unquestionable
claims about the critter. They aren't even sure if it was bipedal or
quadropedal. And even though it was found in a forested environment
it has been pointed out by many that this doesn't mean that is where
it lived. Also, at this point we can't be sure if it is even an ancestor.
At various points in our lineage there have been several separate lines
of hominids (e.g. robustus, boisei, africanus), so it is plausible
that ramidus could be a separate offshoot, too. In fact, if it is
at 4.4 Myr, I would be tempted to think that AAH or no AAH, since this
would leave a tiny amount of time to do all the morphological changes
needed (regardless of the theory).
So ramidus can't be used agaist AAH. I checked. There ain't enough
evidence, or if there is it isn't published yet.
It is
>interesting to note also that the South African site of Langebaanweg on the
>Atlantic coast just north of Cape Town, dating to circa 5 Myr, has no
>hominoid remains despite its wealth of fossil biodiversity (perhaps too far
>south for the Aquatic Ape to swim? I don't know.).
If I knew there were no hominid remains in South Africa I'd tend to
look at this as evidence AGAINST the savannah (and the Tarzan theory,
too? Were there much jungle in S.A. at the time?) It'd be easy for a
savannah dweller to get down there since everything is pretty much
connected, whereas AAH has postulated that the hominids *may* have
been all cooped up on an island.
>I notice that many dogs, especially labradors, are fine swimmers. Was there
>an Aquatic Canine in their ancestry? Maybe that would explain why their fur
>is so much like that of a seal or an otter.
Aren't bird dogs like these *bred* for semi-aquatic behavior (i.e.
swimming out in the marsh to retrieve ducks)? Oh, wait, you're
being sarcastic. ha ha.
>if loss of body hair, acquisition of eccrine sweat glands, etc., arose
>before our ancestors moved into the savannah, and if it is such a poor
>adaptation, why did it survive for at least 3 million years? We have good
>fossil evidence that hominids exploited the savannah (and other environments
>as well) across Africa for the past 3 Myr. That is a long time to live with
>an inadequate adaptation ... certainly natural selection would have had
>ample time to purge our bodies of this aquatic vestige and supplant it with
>a more appropriate adapatation;
I will use the same argument that you savannah use so frequently:
Adaptions aren't always reversable. So once you lost the hair you
can't get it back. And just because a creature doesn't have the
right adaptations for a particular niche doesn't give them a
wild card to get it back. For example, life in the trees could
have been enhanced for apes if they had a tail. Can they grow
it back? No. They have to make do. The savannah ape could have
kept its hair, gotten faster on four legs, and made adaptations
to assist going towards a baboon-type lifestyle. The aquatic
ape had lost most of its hair, was walking upright, and needed
lots of water. It couldn't "purge" these adaptations to get
back to where it started any more than an ape can "purge" its
tail loss. The hominid would have to make do.
AAH says that savannah life would not have *produced* the
morphological changes. But once the changes have been made, could the
creature have survived life on the savannah? Well, if they stuck
close to the rivers and lakes where they hide if predators came, and
if they were able to find a suitable kind of food, they could survive.
They may have known how to use tools and could have led a marrow
scavanging life as postulated by Rob Blumenschine. Life would have
been difficult, but possible.
there are still hairy people around today,
>and if they would have had an advantage in the hot African sun then
>selection would have done its thing rather efficiently. Alternatively, if
>hairlessness etc. was an aquatic adaptation unsuited for inland pursuits,
>and nothing better came along within our genetic capabilities, our ancestors
>probably would have gone extinct and we would not be here to ponder our
>origins.
Who's to say that we weren't more hairless in the past? But something
tells me that once a critter loses its hair it won't grow it back.
For example, the elephant's ancestor has been shown to have been an
aquatic creature, yet it has not regained its hair.
Plus, I suspect that Africa was warm enough for the 3 Myr that
hairlessness wouldn't have led to hypothermia, and that suitable
cooling was available (inefficient as it may have been) to prevent
hyperthermia.
>Bipedal locomotion, eccrine sweat glands, etc, tend to serve human beings
>well. Just ask a hunter-gatherer from the Kalahari desert. It is an
>adaptation that works, and therefore survived the challenges of natural
>selection for the past 3 Myr or more. You may be interested to read the
>research of Chris Ruff (sorry, I don't have a reference handy at the moment)
>who demonstrates the advatages of orthograde posture in maintaining a
>reasonable body temperature.
Exactly. There are humans today more than capable of surviving in the
savannah. But just because something is *possible* does not mean that
it is *advantageous*. What we have been arguing is that the supposed
advantages that the adaptations may have provided to a savannah ape
are either non-existant or questionable. In some cases the adaption,
like sweating, may even be disadvantageous.
Bryce
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