Genetics and the Bear--> Whale Transformation

david ford dford3 at gl.umbc.edu
Thu Aug 7 23:43:16 EST 1997


James G. Acker <jacker at us.net> on 4 Aug 1997 in talk.origins in
      "Rodhocetus (for David Ford)":

> The following three paragraphs are quoted from "New whale from
> the Eocene of Pakistan and the origin of cetacean swimming"
> by Philip Gingerich, S. Mahmood Raza, Muhammad Arif,
> Mohammad Anwar, and Xiaoyuan Zhou,
> 
> Nature, Volume 368, 28 April 1994, pages 844-847:
> 
> "Rodhocetus is important for three reasons.  First, it is an early
> archaeocete that retains high neural spines on anterior thoracics
> and a pelvis articulating directly with the sacrum.  These are
> primitive characteristics of mammals that support their weight on
> land, and both suggest that Rodhocetus or an immediate predecessor
> was still partly terrestrial.  At the same time, cervicals are short,
> enhancing rigidity of the anterior body, sacrals are large but unfused,
> enhancing power and flexibility, and the femur is reduced, stream-
> lining the lumbocaudal trunk.  These are derived characteristics of
> later archaeocetes and modern whales associated with aquatic
> locomotion.  Thus the morphology of Rodhocetus is intermediate,
> as might be expected of a transitional form evolving from land to
> sea."
>      "Second, Rodhocetus is the oldest fossil whale described from
> deep-neritic shelf deposits.  Contemporary and slightly younger whales
> such as Indocetus, which inhabited shallower water, retained long
> hind limbs and fused sacral vertebrae, indicating that there was
> significant morphological and anatomical diversity in early archaeocete
> evolution.  Fossils found in shallow marine environments may not
> represent the full range of this diversity."
>      "Finally, most modern whales have robust lumbar and proximal
> caudal centra, and all lack fusion of sacral vertebrae, making the
> lumbocaudal column seamlessly flexible.  High dorsal neural spines
> and long ventral chevrons limit vertebral excursion but provide leverage
> for powerful axial and abdominal muscles.  Rodhocetus has all of these
> functional features.  This indicates that the characteristic cetacean mode
> of swimming by dorsoventral oscillation of a heavily muscled tail evolved
> within the first three million years or so of the appearance of
> archaeocetes.  Terminal caudals are lacking in the type specimen
> of Rodhocetus and we cannot assess the possible presence of a caudal
> fluke, but it is reasonable to expect development of a fluke to coincide
> with shortening of the neck, flexibility of the sacrum, and reduction of
> hind limbs, first observed in Rodhocetus.  This idea can be tested when
> a more complete tail of Rodhocetus is found."  (End of article)
> 
> ---- end of quotation       
> 
>      David Ford has been provided this information via email and
> has declined to discuss it in terms of whether or not this represents
> a change in body plan via evolution.

If you want me to discuss something, your best bet is to post and e-mail
what you'd like replied to.  I'm a firm believer in open, public
discussion.  The "fact" that all manner of plant and animal structures
came into existence through non-intelligence directed means using
changes in organisms' DNA falls to pieces in the light of genetics, and
that is the angle I'm going to be approaching this claimed discovery of
an intermediate between a land animal and a whale.  Since we'll be
discussing genetics, I've included some appropriate newsgroups.  To
those in those groups, talk.origins is moderated, and if you want your
posts to show up, you might want to put talk-origins at moderators.uu.net
after the "To:" in your e-mail.  I don't like the idea of participating
in a thread named after me, so I've taken the liberty of changing the
title.  The title gets its inspiration from the following remark by
Charles Darwin. 

"In North America the black bear was seen by Hearne swimming for hours
with widely open mouth, thus catching, like a whale, insects in the
water.  Even in so extreme a case as this, if the supply of insects were
constant, and if better adapted competitors did not already exist in the
country, I can see no difficulty in a race of bears being rendered, by
natural selection, more and more aquatic in their structure and habits,
with larger and larger mouths, till a creature was produced as monstrous
as a whale."[_On the Origin of Species_ (1859), original edition, 184.]

>  It is my contention that all of
> the changes described above are modifications of existing structures,
> and therefore there is no obvious genetic barrier to such changes.

"There is no obvious genetic barrier to such changes."  In the
transformation of a land animal into a whale, approximately how many new
genes would you guesstimate were required?  Some areas where new genes
perhaps would be required are in the appearance of the tail fluke, for
any new enzymes or proteins (e.g., perhaps for the whale's skin), for
the new structure that would allow the baby whale to drink milk
underwater, for the cap that is around the nipple, for the organ making
spermaceti, for the muscles and flaps that allow the blowhole to be
closed off when the whale dives, for the baleen filtration system in
baleen whales, for making the mother's milk the composition that it is,
and for the melon.

Geneticists, biologists, please help us out.  Jim and I know precious
little about genetics.  With genes coding for structures, is it
necessary that every nucleotide be present, or else the structure coded
for develops malformed?  For genes coding for proteins, must all the
nucleotides be exactly right?  How many triplet codons typically make up
a structural gene, and how many typically make up a gene coding for a
protein?

>  Mr. Ford is
> therefore invited to quantify the genetic barriers to such changes
> that will preclude such microevolutionary modification of the body
> plan of a terrestrial ungulate into that of a modern, fully-aquatic
> whale.  If he is unable to do so, he will make tacit admission that his
> definition of microevolution encompasses the body plan modifications
> that are seen in the evolutionary transition from four-legged
> terrestrial ungulate to modern whale.   He will also admit that
> Rodhocetus, as stated by the authors, represents an evolutionary
> intermediate in this process.
> 
> Submitted to talk.origins by James Acker, 8/4/97




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