Re: First Family and AAT

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ghanenbu@inter.nl.net (Gerrit Hanenburg) writes:

>hubey@pegasus.montclair.edu (H. M. Hubey) wrote:

>>It could have developed after leaving the water.

>That would mean that the aquatic phase doesn't have much to do with the
>development of the anatomical complex associated with bipedalism.
>I thought that an important point of the AAT was to explain such a
>development.

I wrote it unclearly. I should have said that the development
could have continued after leaving the water.

>Why should the AA walk upright on land instead of moving on all fours like
>it probably did before going aqua?

Head up is the natural position for any land animal that gets
thrown in the water. I assume that the legs would hang down and
that in shallow water they'd be in contact with the bottom. If the
body is more upright (i.e. so-called streamlined) it would be able
to stay in deeper water for the same length appendages.

>>how many years did they spend in water?
>>at what time in their evolution did they go into the water?

>The point isn't how long they have been aquatic or how long ago the
>transition took place.The point is the duration of the transition from
>being terrestrial to becoming aquatic.This can be relatively short.
>About 10 myr in the case of Cetaceans.

Since we cannot perform the experiment of throwing some animal
into the water and keeping it there for 10 million years we can't
tell if any animal will lose its limbs and develop like Cetaceans.

>As far as I now it has been fairly well established that Cetaceans have
>descended from Eocene mesonychid condylarths about 45-55 myr ago.
>The mesonychids were terrestrial quadrupeds with fully developed hindlimbs.

Full developed as in dogs, humans, horses, or say crocs and lizards?

>Intermediate fossils have been discovered,such as:Pakicetus,Ambulocetus,
>Rodhocetus and Basilosaurus.There is a progressive reduction of the
>hindlimbs.

OK. I still find it difficult to believe that humans can assume
the shape of whales. Maybe webbing will develop on hands and feet.
maybe the digits will get even longer. But this is more like
science fiction.

-- 


Regards, Mark


http://www.smns.montclair.edu/~hubey

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