Contra AAT

Gerrit Hanenburg (
Thu, 6 Jul 1995 19:31:25 GMT

What about this:

Organisms that spend much of their time in (at least) chestdeep
water will be selected to make use of Archimedean Law in an
efficient way.I think that is by floating and/or swimming,not by
walking upright.Walking upright is not an efficient way of getting
around in chestdeep water.
It is not the right environment to select in favour of an anatomical
complex that suits bipedal locomotion because the upward pressure
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.
Without those gravitational forces there is no selection to remodel the
lower body in favour of bipedalism.Instead you would expect a kind
of "degeneracy" or remodeling in the direction of wateradapted
locomotion.(i.e swimming and/or floating).
Other mammals that have moved to the water have lost their hindlimbs
altogether as in whales,dolphins and manatees or they have
become much less functional in terrestrial locomotion as is the case
in pinnipeds,and where they kept their legs they became adapted to
swimming as in otters(webbed feet).
On these grounds I think it is unlikely that an anatomical change in
the direction of bipedalism (on land) will begin to develop in an aquatic
environment as proposed in the AAT.