The first whales

From: Howard Garrett (tokitae@orcanetwork.org)
Date: Tue Nov 27 2001 - 15:20:32 EST


>I am fasinated with whales. I have got lots of information about whales
>but I haven' t got any about what whales evolved from. I have been
>watching walking with beasts and it told us a little about the earliest
>whales in programme 1 but I can't remember the information about them.
>Please send me all the information you know about the earliest whales.
>
>Thanks,
>Alex Lucas (age 10)

         I too am fascinated with whales, so I'm happy to discuss them with
you. Your question is very timely because there has been some new
information about whale evolution just recently. Below is the abstract of a
breakthrough development in the study of whale evolution. It's a wonderful
demonstration of how science progresses by the rules of empirical
methodology, and old assumptions are overturned by new evidence. I know
some of the words will be new for you, but I'll summarize the results, and
maybe your parents or teacher can help you with the big words.

         A few years ago it was believed the whales evolved from a dog-like
animal, a carnivore with sharp teeth. Then some DNA studies showed that
sperm whales, which have very large teeth, were more closely related to
baleen whales, which have no teeth, than they were to the other toothed
whales. That didn't make sense at the tim. But now this new discovery shows
that the earliest whales are actually descended from some kind of
artiodactyl (grazing animals), although they don't know what it looked
like. So the first whales were not meat-eating predators, but were more
inclined to graze through concentrations of plankton, like copepods and
krill, and so they probably first evolved some kind of filter feeding
ability. That means the toothed whales evolved in several branches from the
baleen whales, which explains why sperm whales are more closely related to
baleen whales than they are to toothed whales like orcas.

         There are new discoveries all the time in whale research, and
there are plenty of important questions still unanswered for future whale
scientists.

Thewissen, J. G. M.; E. M. Williams; L. J. Roe and S. T. Hussain. (2001).
Skeletons of terrestrial cetaceans and the relationship of whales to
artiodactyls. Nature (London) 413(6853):277-281. 2001.
Abstract: Modern members of the mammalian order Cetacea (whales, dolphins
and porpoises) are obligate aquatic swimmers that are highly distinctive in
morphology, lacking hair and hind limbs, and having flippers, flukes, and a
streamlined body. Eocene fossils document much of cetaceans' land-to-water
transition, but, until now, the most primitive representative for which a
skeleton was known was clearly amphibious and lived in coastal
environments. Here we report on the skeletons of two early Eocene pakicetid
cetaceans, the fox-sized Ichthyolestes pinfoldi, and the wolf-sized
Pakicetus attocki. Their skeletons also elucidate the relationships of
cetaceans to other mammals. Morphological cladistic analyses have shown
cetaceans to be most closely related to one or more mesonychians, a group
of extinct, archaic ungulates, but molecular analyses have indicated that
they are the sister group to hippopotamids. Our cladistic analysis
indicates that cetaceans are more closely related to artiodactyls than to
any mesonychian. Cetaceans are not the sister group to (any) mesonychians,
nor to hippopotamids. Our analysis stops short of identifying any
particular artiodactyl family as the cetacean sister group and supports
monophyly of artiodactyls.



This archive was generated by hypermail 2b30 : Mon Feb 25 2002 - 21:06:00 EST