AAT : the cop-out?.
Elaine Morgan (Elaine@desco.demon.co.uk)
Thu, 17 Aug 1995 15:24:58 GMT
Frist can I dispose of three questions left dangling..
1. If the ape did so well out of the sea, why did it levae
it?
The sea left the ape ; it became unlivable in and
evaporated.
2. How could an aquatic ape get marooned on an island? Not.
It was an arboreal ape that got marooned, a group of the
last common ancestor.
3. Lucy's phalanges. Okay, most primates have straight
phalanges. I'd imagine their ancestore never brachiated.
My only point was that once the fingers had become
curved,there'd be no great selection pressure to straighten
them unless the hominid became a ground-runner, which we
agree is unlikely. We also agree Lucy spent some of her time
in the trees. So any staightening process would be very
slow.
Now can we get down to brass tacks on aquatics and
skeletons. The search for a "fusiform" ape is quite absurd.
Let's try to get our minds away from mermaids.
We are told AAT is rubbish because the first sign of aquatic
habits is that legs get shorter, and ours have got longer.
Of course most of the lengthening was post-Lucy. But quite
apart from that, there is no such rule. It depends what
you're doing in the water. Think about waders. Think about
cranes and herons. A moose spends a lot of time in water.
Its legs are longer than those of most ungulates, not
shorter. Look at the only flooded-forest-dwelling African
ape, the bonobo. It has relatively longer legs than its
nearest kin and is almost identical in this respect to Lucy.
Think about diet. If a carnivore like a wolf goes aqauatic,
its instinct tells it to chase things that run away and grab
them in its jaws. It will adapt by catching fish, which
means its best hope of a meal is spending the maximum time
under water and swimming very fast like a dolphin. It will
ultimately lose its limbs.
If a grazer goes aquatic and eats underwater plants it will
grow slow and lazy, but also spend most of its time
submerged is a weightless medium. It will ultimately lose
its legs.
What happens if a primate opts to, or is forced to, live on
sea-food? We don't have to guess, through guessing wouldn't
be hard. It might eat crustaceans, like the crab-eating
macaque. Better still look at Koshima, where 100 macaques
are stuck on an island half a mile across. They follow their
natural primate instincts and look for things they can pick
up in their hands. They scavenge dead fish. They pick large
limpets off the rocks and eat them. Quote from a tv
documentary: "In the morning they are all out
beach-combing...Here a big octopus is claimed by the troop's
top male..One monkey begs for a share, the rest gather
gather other windfalls for themselves..(at midday)
When the sand starts to burn their feet, they retreat to the
forest where there is plenty of shade". Three times a week
they get fed sweet potatoes by scientists, otherwise they
would be even more dependent on the seafood. If a potato
floats out to sea they swim out and retrieve it.
This kind of behaviour is never going to remould an animal
into a torpedo. It may tend to make it stand up straighter.
(they often wade in bipedally, whether they are carrying
anything or not. But it's never going to turn their arms
into flippers. It's never going to make their back legs
disappear. It's never going to move their nostrils to the
top of their heads. Scavanging for sea food is a much better
option than scavenging for land food ( a perfectly
respectable conventional hypothesis) because the tide brings
in fresh supplies twice a day. Their hands and arms and
fingers are far more useful to them used for this purpose
tha they would ever be as mere propellors.
How would any scientist, by studying the skeletons alone,
deduce that a hippo was more aquatic than a rhino, an otter
than a ferret, a fish-eating mongoose than a snake-eating
one?
The only practical question here is whether a degree of
aquaticism which does not radically modify the skeleton
(since you reject the bipedalism argument) might
nevertheless account for other changes we have noted in
skin, respiratory canal, etc. It is perfectly conceivable.
Compare a pelican with a penguin. The pelican does not spend
any part of the year almost continually submerged, so it has
not become torpedo-shaped and it has not turned its wings
into flippers. It does assume a streamlined posture during
a dive, but a visit to the nearest pool will confirm that
Homo sap. does the same. But note: it has acquired perfect
breath control, and a triangular moveable flap in its throat
which is a fairly good analogue of our own (unique) moveable
velum.
Again, a babyrusa likes to live in swamps. There is nothing
in its skeleton to prove it is any more aquatic than a
wart-hog; but its skin is hairless. The water-buffalo too
has lost most of its hair for a similar reason.
The apes may at some time have had to spend a lot of time in
the water, as some Japanese macaques spend time in the hot
springs, but for the opposite reason - not to keep warm,
but to keep cool, just as the hippo does. That may have been
true not only during the initial phase but continuing on
into the svannah-mosaic phase. Afar is one of the hottest
spots on earth. Wallowing in the Awash could have gone on
radically affecting their skin while having no effect at all
on their bones.
I am frankly baffled by all this. What do you want of me?
What are the signs you wanted me to predict? I mean -
"fusiform"? Surely you cannot be serious?
The falsifier?
By far the most deadly threat to my personal AAT scenario
(there are other versions; Lyall Watson favoured a site at
the south end of the Rift valley) was posed by Harry Erwin.
He says that my timing does not coincide with similar events
in the Med and the Red Sea. I admit the weakest link in my
case is a vagueness about the dates of successive
sea-floodings. It is not necessarily my fault. The
conventional accounts, while going into immense detail about
the ecological background of inland sites, for the most part
*never mention* what was going on in the Afar triangle. So
evidence is sparse. But I will append some quotes from a
recent three-part tv series on the Great Rift; it was
presented from a wholly conventional standpoint and starring
the Laetoli prints.
"The Danakil Depression is ..the epicentre of the Great
Rift. It used to be the bottom of the sea.." (then it
evaporated ) "This happened again and again".
It talks of "a chain of salt-saturated depressions", and of
Lake Asal. to the north of the volcano Adukuba. It says the
presence of the lake seems at first incredible -"a
disconnected salt-encrusted body of water in the middle of
the hottest and driest of deserts. But the water is coming
from the sea, the sea being under Adukuba and its lava
field".
It shows a crack in the earth which is "widening so fast
that you can put a stick across in the morning and by the
evening it has fallen in. Someday the rupture will be
complete. The sea will break through and a new valley will
be populated by reefs and fishes. And not for the first
time".
I had imagined the sea breaking in from ouside. In that case
what was happening in the Med would have been vital
evidence. But the rifting of the Rift is apparently
unconnected with ice ages and sea levels. If a widening
crack can cause the sea to come up from underneath, we are
into a whole new ball game.
Elaine
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