Re: First Family and AAT

Gerrit Hanenburg (
Wed, 27 Sep 1995 10:43:30 GMT (H. M. Hubey) wrote:

>>of the water takes much of the load of the body off your lumbar spine,
>>pelvis and lower limbs.That load is exactly what is needed to remodel
>>the anatomical complex of an arboreal ape into that of a bipedal ape
>>that walks on land.

>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

Why should it have developed 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?

>>Other mammals that have moved to the water have lost their hindlimbs
>>altogether as in whales,dolphins and manatees or they have

>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.

>Even the whole idea of why appendages developed is not
>"explained". One could sort of try going backwards.

>Perhaps these animals (whales, dolphins) were never fully
>land animals to begin with and that they always lived near
>the shore and were aquatic and that their "legs" never
>fully developed, instead of looking like other mammals
>like dogs/cats who lost their legs after going into the water.

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.
Intermediate fossils have been discovered,such as:Pakicetus,Ambulocetus,
Rodhocetus and Basilosaurus.There is a progressive reduction of the
I do not expect the anatomical changes in the aquatic ape to be as
pronounced as in whales,since whales are fully aquatic and the aquatic ape,
as I understand it,was semiaquatic.But in a million years of semiaquatic
life I do expect some changes,and not only in the soft tissues but also in
the bones because to natural selection there is no difference between
"soft" and "hard".In evolution bone is as plastic as any other tissue.