Yes Virginia, birds ARE dinosaurs

["N. MacLeod" <N.MacLeod@xxxxxxxxx>]

There is a semantic question here, but I think it is more subtle than the
one Erich Rose suggests. From a phylogenetic point of view birds ARE
dinosaurs, snakes ARE lizards, humans ARE apes, and all three ARE
tetrapods. The colloquial designation of these groups as separate entities
reflects an earlier systematic philosophy that did not take evolutionary
processes into account in establishing the group definitions; or at least
didn't take it into account as fully as is the trend among most present-day
systematists. The semantic difficulties come when people try to force one
nomenclatural convention on others simply because it is their personal
preference or because it makes sense in certain contexts. Suffice it to say
that there are contexts in which it is advantageous (in terms of the
questions being asked) to recognize that birds have different morphologies,
ecologies, etc. from the non-avian dinosaurs, and other instances in which
it is advantageous to focus on the characters that unify birds and
non-avian dinosaurs. This decision will depend on the particular research
problem under investigation. However, since there is a copious amount of
data demonstrating the link between birds and dinosaurs, to conclude that
birds are somehow members of a different group simply because they possess
certain autapomorphies or are more commonly found in trees than on the
ground is tantamount to saying that humans are not apes because we have
differently-shaped heads or that we are more commonly found in front of the
TV.

For example, it might strike some people as amazing that certain non-avian
dinosaurs made nests, assembled those nests in groups (= rookeries), and
cared for their young. Certainly we don't see that sort of behavior in many
other reptilian-grade tetrapods. Others, however, would point out that this
behavior might not be as unusual as it might otherwise appear since it is
common among many bird groups which are the lineal descendents of non-avian
dinosaurs. Indeed, an appreciation for the phylogenetic relations between
birds and non-avian dinosaurs might even suggest that such behaviors as
nesting, rookery formation, and certain aspects of feeding/caring for young
are not "bird" characteristics at all but reflections of dinosaur behavior
patterns. It is difficult for me to see how anyone can label ways of
looking at natural history phenomena that demonstrably expand the types of
questions we can ask and the manner in which those questions can be
answered as "BAD SCIENCE;" especially since phylogenetic systematics is the
dominant school of systematics in the world today. Adoption of a strictly
phylogenetic point of view is not a panacea, but neither is it some
nefarious plot hatched by unscrupulous, attention-seeking
paleontologists/biologists.

The mural example strikes me as a similarly subtle semantic argument. The
Zallinger mural (and others like it) can be faulted for many things (see
Rudwick 1992, Gould 1993), but it is a work of art, not a treatise on
evolution. The ceiling of the Sistine Chapel, Botticelli's "Birth of
Venus," Gerome's "Pygmalion and Galatea", Dali's "Persistence of Memory,"
etc. all contain their share of factual errors, but these are used by the
artists to make a larger points. In the same way, Zallinger used the
metaphor of the landscape to make a point about changing biotas over time.
Personally, I've always found the substitution of space for time in the
Zallinger mural quite satisfying in that there is an intriguing duality
between the concepts of space and time in much of evolutionary theory
(e.g., the allopatric speciation concept). As with the phylogenetic vs.
'evolutionary" systematics controversy, the semantic danger here, is to
assume that there is only one "correct" way to look at natural history art.
I've heard the same sorts of criticisms raised about the factual errors in
"The Flintstones" and the "Dinosaurs" TV programs.

Norm MacLeod


Gould, S. J. 1993. Reconstructing (and deconstructing) the past. Pp. 6-21
in Gould, S. J., eds. The Book of Life. W. W. Norton & Co., New York.

Rudwick, M. J. S. 1992. Scenes from Deep Time. University of Chicago Press.
Chicago.




>
>I realize this is a big can-o-worms but here goes:
>
>What do you(anyone interested) think of the birds-ARE-dinosaurs concept?
>
>The reason I ask is because it strikes me as very "gimmicky" and most often
>is used for it's buzz word value(see below). The general public goes wow
>and scientists get some attention payed to them and all is warm and fuzzy.
>But obviously birds are not dinosaurs. They may be VERY closely related and
>may share a common ancestor but a dinosaur is not a bird.
>
>We don't call snakes lizards even though they are very closely related. We
>have not gone backwards and decided to call snakes "lizards" just because
>we have a better idea of their evolutionary heritage. The point is that
>even though birds may have evolved from therapod dinosaurs, the fact is
>that they EVOLVED into BIRDS. BIRDS. BIRDS. BIRDS.
>
>By playing on symantics(buzz words) here the Paleontological community is
>practicing BAD SCIENCE. Bad science is an incidious thing. It often comes
>in the form of overly simplified ideas or images. One of my favorites is
>the ubiquitous illustration of the Mesozoic as a long stretched out mural
>with something like a Dimetrodon at one end crawling around the swamp and a
>big'ol T-rex at the other kicking up the dust in a desert setting.
>Somewhere in the jungle between we have some brontos and duckbills and so
>forth. Now you and I know that this is not the image of one point in time
>and space(we are biased in our knowledge of natural history) but the
>average museum visitor or youngster scanning through library books thinks
>that all of these critters lived together at the same time. It's a nice
>mural but it's bad science.
>
>The idea of communicating to the lowest common denominator is not exclusive
>to television.
>
>With the upcoming release of "Lost World" I shudder at what we are in store
>for next.
>
>I hope for some interesting discussion.
>
>Erich Rose
>
>PS I am an exhibit designer by day which is why I am so intersted in this
>subject. That is to say the problem with bad science, not Birds are dinos,
>and being an amateur geology and paleontology buff may bias me a bit toward
>this particular subject.




___________________________________________________________________

Dr. Norman MacLeod
Micropalaeontological Research
N.MacLeod@nhm.ac.uk (E-mail)

Department of Palaeontology, The Natural History Museum,
Cromwell Road, London, SW7 5BD

Office Phone: 0171-938-9006
Dept. FAX: 0171-938-9277
E-mail: N.MacLeod@nhm.ac.uk
___________________________________________________________________