Re: new description of the AAT group


To be honest I haven't studied ATT that much. However, if one accepts
the following that mammals descended from rodents this would appear to
contradict ATT. I came across the following article:


DNA evidence settles debate on mammal origins
Friday, 2 February 2001



Settled: Fruit bats are not more closely related to primates than to
other bats.
Humans are closer to rats than they are to any other distant relatives,
according to new research which claims to settle a number of hot
debates on the origin of mammals.

Two independent international research efforts reported in this week's
Nature have analysed the differences and similarities in DNA sequences
of a large number of placental mammals (the group of species which
includes humans). Despite using different data, both studies have come
up with the same patterns of relationships between species.

"It's very impressive work," says Dr Steve Donnellan from the Museum of
South Australia. "It's the first time that the power of genomics has
been used to look at a series of long standing problems surrounding the
origin of mammals."

The evolutionary history of the placental mammals has provided grounds
for scientific debate as acrimonious as you would find anywhere. Over
the past decade, evolutionary biologists seeking to reconstruct the
evolutionary relationships of placental mammals using DNA and molecular
evidence have often locked horns with scientists using an approach
based on careful study of bones, teeth and anatomy.

The DNA studies have often resulted in glaring discrepancies, however,
the two new studies in Nature overcome many of the inadequacies of the
earlier studies by analysing data from a large number of genes from a
large number of species.

Donnellan says one of the debates settled by the research is the
relationship of flying foxes to other bats. Scientists looking at the
anatomy of the eye have recently proposed that these large fruit-eating
bats are more closely related to primates than to other smaller
insect-eating bats.

"This research has put that hypothesis to bed," says Donnellan. "It
clearly shows that all bats are more closely related to each other than
anything else." In fact bats were found to be closer to pigs and cows
than to rodents and primates.

The molecular research also favours a closer relationship between
primates and rodents, and between whales and hippopotamuses than
previously thought.

Another interesting consequence of the research is that many
adaptations seen in placental mammals, ranging from aquatic habit to
flight, evolved many times independently.

"Up until now, we've really only had mickey mouse approaches to
studying these questions," says Donnellan. "Now, we are able to use the
data waterfall that's coming out of genome research".

Gondwanan origins
The new molecular research also gives new life to a 19th Century idea
that a very eclectic group of animals which includes elephants, dugongs
and aardvarks are all closely related and probably originated in
Africa.

According to Professor Tim Flannery of the Museum of South Australia
the findings also support a controversial theory advanced by himself
and Dr Tom Rich of the Museum of Victoria that placental mammals
originated in the Southern Hemisphere.

He says that changes in DNA sequences occur at a rate that can be used
to calculate the divergence of various evolutionary pathways. Applying
this "molecular clock" to this most recent data, he says, supports the
idea that placental mammals originated 120 million years ago during the
age of the dinosaurs.

Flannery and Rich have reported the discovery of placental mammal
fossils of this age in Southern Victoria. Their theory challenges the
idea that placental mammals orginated in the Northern Hemisphere much
later - around 65 million years ago.

Dr Don Colgan from the Australian Museum in Sydney, however, is not so
convinced suggesting the "molecular clock is too sloppy" to draw such
conclusions about the age of species. He instead prefers to focus on
the ability of DNA to describe the relationships between species.

"The research demonstrates the maturity of molecular evolutionary
biology," says Colgan. "The degree of agreement between the two
different data set is outstanding. You couldn't get the same sort of
agreement using two sets of morphological data."


Anna Salleh - ABC Science Online

You state, "You must have noticed that we made the distinction between:

- AAT broad sense (aquarboreal apes theory) = Mio-Plicene aquarboreal
apes
in swamp forests = wading (swimming?) vertical-clmibing.
- AAT strict sense (amphibious ancestors) = Plio-Pleistocene littoral
Homo
along shores = wading diving for seafood beach-combing (first out of
Africa?)."

If we evolved from Rodentia as the article suggests and as Mr. Tyler
has apparently alluded to could we have made this transition to Homo
while still in the water? Merely wading and diving for seafood beach
combing doesn't to my mind necessarily suggest that. We could have
evolved from Rodentia on land yet still retained characteristics which
allowed us to swim and wade and dive for sea food beach combing.
Snorkling is a simple apparatus and I'm sure our evolutionary ancestors
were capable of constructing primitive snorkeling apparatus.

Make no mistake. I believe every form of life on earth can be traced
back one way or another to the oceans. There may be some who dispute
that and there may even be evidence I'm wrong. I'm not aware of any.But
certainly some evolutionary species continued to evolve on land and
some evolved in the water, on land, and then back in the water again.
And some species have evolved in the water. I just don't think Homo
developed in the ocean. Instead I think "we" started out in the ocean
as a species (actually several "species" which evolved in the oceans)
and this was a transitional evolutionary process which resulted in us
evolutionarily developing to Hominids on land. We may have even
evolutionarily developed over time in the oceans then onto the land and
then back in the oceans again and then onto land again.

I doubt rodents who partially spend their time in water to a large
degree and also capable of being on land would evolve to a mammal due
to the ocean but more as a result of being on land and gradually
adapting to it to the point they left the water completely.

Sincerely,
Michael Ragland


.

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