bertrand@eiffel.UUCP (Bertrand Meyer) (04/15/91)
Here are some extracts from an article entitled ``Dinosaur Dilemmas'' by John Maynard Smith, Professor of Biology at the University of Sussex, appearing in the latest issue of the New York Review of Books, dated April 25, 1991. The article is a review of two recent books on dinosaurs. --------------------------- Begin quote ------------------------------ The interpretation of [dinosaur] fossils is primarily aimed at recognizing anatomical similarities and differences, and arranging the specimens into a natural classification. [...] Today, a ``natural classification'' is usually taken to mean one that reflects evolutionary history. If species are grouped together in a ``taxon'' (that is, a genus, family, order, or what have you), the implication is that the taxon includes all species, and only those species, descended from a common ancestor. [...] It is clear from reading ``The Dinosauria'' [a book published by the U. of California Press] that an important change for the better has taken place since I was a student, although the new dispensation too will become an abuse if we do not watch it. The name of the change is ``cladistics.'' This is one of two very different approaches that have been made in recent years to devise a rationale for classification. The first was numerical taxonomy. Robert Sokal and Peter Sneath, the founders of numerical taxonomy, took the simple way out. If there is no good reason for preferring one trait to another, let us, like good democrats, treat all traits equally. When classifying a set of animals, write down everything about them, in as mindless a way as possible. Then write a computer program that will group together those species that are alike in most respects. It was a method only possible with the advent of computers. It had the great merit that there was no damned judgment about it. In practice, however, numerical taxonomy has been largely replaced by cladistics, essentially, I believe, because Sokal and Sneath insisted that classification should be independent of evolutionary considerations. Cladistics was invented by an East German taxonomist, Willi Hennig. [...] There are two components to the method, one substantive and one semantic. The substantive component concerns which traits are important when classifying, if one wishes one's classification to reflect evolution. The rule is that one should use ``shared derived characters'': there are some impressive Greek words for these that I won't bother with. For example, zebras and horses have a single toe, whereas opossums and humans have five toes. To have five toes is not evidence of close relationship, because it is the primitive condition in land vertebrates; but having a single toe is good evidence of relationship, because it is a recently evolved state. The hard question, of course, is how to decide which is the primitive and which the derived state. If we had a perfect fossil record, there would be no problem: but if we had a perfect record, classification would be trivially easy anyway. [...] [The] other, semantic component of cladistics [...] asserts that any named taxon - for example, Eutheria (placental mammals), Dinosauria, Lacertilia (lizards) - must be monophyletic; that is, it must include all, and only, the descendants of a single common ancestor. Notice that, according to this requirement, Pisces (fish) is not a valid taxon, because it does not include the land vertebrates, which are descended from fish. Consistent with this view, the editors include the birds among the dinosaurs, as they must on cladistic grouds, because the birds are thought to be descended from a particular group of small carnivorous dinosaurs. --------------------------- End quote -------------------------------- -- -- Bertrand Meyer Interactive Software Engineering Inc., Santa Barbara bertrand@eiffel.uucp
chl@cs.man.ac.uk (Charles Lindsey) (04/15/91)
In <527@eiffel.UUCP> bertrand@eiffel.UUCP (Bertrand Meyer) writes: >Here are some extracts from an article entitled ``Dinosaur Dilemmas'' >Consistent with this view, the editors include the birds among the >dinosaurs, as they must on cladistic grouds, because the birds are >thought to be descended from a particular group of small carnivorous >dinosaurs. Ergo, mammals are dinosaurs also, and hence so are we.
rick@tetrauk.UUCP (Rick Jones) (04/16/91)
In article <chl.671706575@m1> chl@cs.man.ac.uk (Charles Lindsey) writes: |In <527@eiffel.UUCP> bertrand@eiffel.UUCP (Bertrand Meyer) writes: | |>Here are some extracts from an article entitled ``Dinosaur Dilemmas'' | |>Consistent with this view, the editors include the birds among the |>dinosaurs, as they must on cladistic grouds, because the birds are |>thought to be descended from a particular group of small carnivorous |>dinosaurs. | |Ergo, mammals are dinosaurs also, and hence so are we. I'm not a zoologist, but I always understood that the mammals were an entirely separate species which evolved during the dinosaur era, and only flourished after the dinosaurs' decline. This doesn't have much to do with this newsgroup, except perhaps to illustrate that thorough knowledge and extensive research are a pre-requisite to the effective design of hierarchies. -- Rick Jones, Tetra Ltd. Maidenhead, Berks, UK rick@tetrauk.uucp Any fool can provide a solution - the problem is to understand the problem
drdan@SRC.Honeywell.COM (Dan Johnson) (04/17/91)
In article <chl.671706575@m1> chl@cs.man.ac.uk (Charles Lindsey) writes: >In <527@eiffel.UUCP> bertrand@eiffel.UUCP (Bertrand Meyer) writes: > >>Here are some extracts from an article entitled ``Dinosaur Dilemmas'' > >>Consistent with this view, the editors include the birds among the >>dinosaurs, as they must on cladistic grouds, because the birds are >>thought to be descended from a particular group of small carnivorous >>dinosaurs. > >Ergo, mammals are dinosaurs also, and hence so are we. Nope, mammals are evolved from therapsids, which evolved (along with dinosaurs) from reptiles. (It's amazing what you learn because of a 5-year-old with an insatiable curiosity about dinosaurs.) Daniel P. Johnson Honeywell Systems and Research Center e-mail: drdan@src.honeywell.com phone: 612-782-7427 office: 2433 fax: 612-782-7438 Mac Mail: "Johnson Daniel" voice: "Yo, Dan!" US mail: MN65-2500, 3660 Technology Drive, Minneapolis, MN 55418
chl@cs.man.ac.uk (Charles Lindsey) (04/17/91)
In <1135@tetrauk.UUCP> rick@tetrauk.UUCP (Rick Jones) writes: >|Ergo, mammals are dinosaurs also, and hence so are we. >I'm not a zoologist, but I always understood that the mammals were an entirely >separate species which evolved during the dinosaur era, and only flourished >after the dinosaurs' decline. Yes, but the first mammal had to evolve from something, and that something was a dinosaur.
rh@smds.UUCP (Richard Harter) (04/20/91)
In article <chl.671877660@m1>, chl@cs.man.ac.uk (Charles Lindsey) writes: > In <1135@tetrauk.UUCP> rick@tetrauk.UUCP (Rick Jones) writes: >>|Ergo, mammals are dinosaurs also, and hence so are we. >>I'm not a zoologist, but I always understood that the mammals were an entirely >>separate species which evolved during the dinosaur era, and only flourished >>after the dinosaurs' decline. > Yes, but the first mammal had to evolve from something, and that something > was a dinosaur. It is puzzling to me why this is here, rather than in talk.origins which is the natural home of bogus science. Perhaps the intent is to illustrate the consequences of erroneous class inheritance. In any case: The mammals evolved from the therapsid reptiles. The dinosaurs evolved from the thecodont reptiles. The two branches are not closely related. Birds may have evolved from the coelosaurian dinosaurs or from the pseudosuchian reptiles [kin to the thecodonts]. There is still a lively debate going on about the origin of birds. -- Richard Harter, Software Maintenance and Development Systems, Inc. Net address: jjmhome!smds!rh Phone: 508-369-7398 US Mail: SMDS Inc., PO Box 555, Concord MA 01742 This sentence no verb. This sentence short. This signature done.
Kai_Henningsen@ms.maus.de (Kai Henningsen) (04/21/91)
CL>>|Ergo, mammals are dinosaurs also, and hence so are we. CL> CL>>I'm not a zoologist, but I always understood that the mammals were an entir CL>>separate species which evolved during the dinosaur era, and only flourished CL>>after the dinosaurs' decline. CL> CL>Yes, but the first mammal had to evolve from something, and that something CL>was a dinosaur. I think not - it was a reptile, I believe, like the first dinosaur :-) So, we and the dinosaurs are both reptiles (and hence fish, vertebrate, whatever ...). Humm, does this make us all monocellulars? MfG Kai
diamond@jit345.swstokyo.dec.com (Norman Diamond) (04/22/91)
In article <405@smds.UUCP> rh@smds.UUCP (Richard Harter) writes: >In article <chl.671877660@m1>, chl@cs.man.ac.uk (Charles Lindsey) writes: >>In <1135@tetrauk.UUCP> rick@tetrauk.UUCP (Rick Jones) writes: >>>|Ergo, mammals are dinosaurs also, and hence so are we. >>>I'm not a zoologist, but I always understood that the mammals were an entirely >>>separate species which evolved during the dinosaur era, and only flourished >>>after the dinosaurs' decline. >>Yes, but the first mammal had to evolve from something, and that something >>was a dinosaur. >It is puzzling to me why this is here, rather than in talk.origins which >is the natural home of bogus science. Well, meta-discussions about possibly mistaken science are different from possibly mistaken science, and possibly mistaken science is different from pure garbage, so it's not clear that talk.origins is the correct place. >Perhaps the intent is to illustrate >the consequences of erroneous class inheritance. This seems very likely, considering how this thread got started. Do you realize who you were flaming? For a hint, look at the references line, and for another hint, ... uh, I can't exactly say take a leap of "faith," but you know what I mean. -- Norman Diamond diamond@tkov50.enet.dec.com If this were the company's opinion, I wouldn't be allowed to post it.
kers@hplb.hpl.hp.com (Chris Dollin) (04/22/91)
Charles Lindsey says: Yes, but the first mammal had to evolve from something, and that something was a dinosaur. References? [The dinosaurs were not the *only* species around at the time; what makes you think it was from them that the mammals evolved. I understood that the ancestral mammal was around at the time, anyway. What little I know about the issue has been distorted from Stephen Jay Gould's ``popular'' books.] -- Regards, Kers. | "You're better off not dreaming of the things to come; Caravan: | Dreams are always ending far too soon."
richieb@bony1.bony.com (Richard Bielak) (04/22/91)
In article <chl.671877660@m1> chl@cs.man.ac.uk (Charles Lindsey) writes: >In <1135@tetrauk.UUCP> rick@tetrauk.UUCP (Rick Jones) writes: [...Mammals are a] >>separate species which evolved during the dinosaur era [...] ^^^^^^^ I don't know the precise term, but mammals are a separate group (family?). There are many different species of mammals. >Yes, but the first mammal had to evolve from something, and that something >was a dinosaur. No, no, no! Disnosaurs and mammals are both vertebrates and have evolved from a common ancestor. But mammals did *NOT* evolve from dinosaurs. Please read your Darwin! In Eiffel we would have ;-) : class DINOSAUR is inherit BACKBONE features ... end; and class MAMMAL is inherit BACKBONE features ... end; ...richie -- *-----------------------------------------------------------------------------* | Richie Bielak (212)-815-3072 | Programs are like baby squirrels. Once | | Internet: richieb@bony.com | you pick one up and handle it, you can't | | Bang: uunet!bony1!richieb | put it back. The mother won't feed it. |
guest@alfrat.uucp (Mr. Guest User) (04/23/91)
Aha! finally in this dinosaur business there has been a mention of something to do with Object Oriented Concepts. I refer to Richie Bielaks article <1991Apr22.125642.7488@bony1.bony.com>. It's a pity that there is a slight mistake in the example he gives. In article <1991Apr22.125642.7488@bony1.bony.com> richieb@bony1.UUCP (Richard Bielak) writes: >No, no, no! Disnosaurs and mammals are both vertebrates and have --- ----------- > >In Eiffel we would have ;-) : > > class DINOSAUR is > > inherit > BACKBONE > features > ... > end; Oops! Does this mean a DINOSAUR is a BACKBONE? I hope he meant to say that a DINOSAUR inherits from something that has a BACKBONE, like maybe a vertebrate.
ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe) (04/26/91)
In article <308@alfrat.uucp>, guest@alfrat.uucp (Mr. Guest User) writes: > Aha! finally in this dinosaur business there has been a mention of something > to do with Object Oriented Concepts. I'd like to point out that biological classifications do have something to teach us. The key idea of "cladistics" is to base taxonomies on actual lines of descent, and the groups thus formed are monophyletic. To put it another way: SINGLE INHERITANCE. The techniques were not designed to be useful when multiple inheritance (e.g. transfer of genetic information by viruses from one bacterial strain to another) is significant. There is another lesson: cladistic classifications break up "traditional" groups which have a fair bit of heuristic power. Consider, for example, Gould's article "What, if anything, is a Zebra?" in which he explains how the traditional category "zebra" (horse-with-stripes) contains species from two separate groups. Fine, so "zebra-ness" is not something that was inherited from a common ancestor. That doesn't mean it isn't a useful category. Horse-like animals with stripes clearly inhabit a different ecological niche from horse-like animals of a solid colour, and it's quite likely that we cluster information about habitat, diet, predation, &c rather better using zebra/horse as our categories than if we used the "real" evolutionary divisions. Similarly, "fish" is not a valid category if you are solely concerned with actual lines of descent, but those sort-of-cylindrical non-homeothermic vertebrates that live in water _do_ have a lot in common with each other that they don't have in common with creatures which are "closer" in a cladistic classification. One lesson to be learned from this is that there may be >no< "right" classification system. If you have classes A, B, and C, with B derived from A, it may still be the case that B and C have more in common than A and B. This is one reason for multiple inheritance. -- Bad things happen periodically, and they're going to happen to somebody. Why not you? -- John Allen Paulos.