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Author Topic:   Dogs will be Dogs will be ???
crashfrog
Member (Idle past 1581 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


(2)
Message 286 of 331 (654038)
02-26-2012 10:32 AM
Reply to: Message 281 by Chuck77
02-26-2012 6:13 AM


Taxonomy
I think it would be good to start by the certain catagories already set in place and go from there maybe.
When thinking about classification of animals - the study of which is called taxonomy - it's helpful to understand what actual problem taxonomists are trying to solve.
Here's an animal:
What is it? Well, that depends on who, and where, you ask. Dutch Afrikaans would call it the "earth wolf", or, in Dutch, the "aardwolf." Does that mean it's a wolf? Well, another name for it is "maanhaar jackal." So is it a jackal? And, of course, other people may call it something else. It's frequently mistaken for a hyena, so locals may refer to it as the "stripey hyena."
It's not uncommon for different people living in different places to have different names for the same plant or animal, and by the 1700's, when the "natural sciences" were really taking off, this was becoming a huge obstacle to effective communication about plants and animals, especially due to an enormous number of name collisions, where different populations were using the same name for different plants and animals. It was a mess!
So scientists wanted a set of systematic names for things, such that each species (which they really did think of back then as a "kind", a discrete and separate form of living thing) had its own systematic name, unique to it and descriptive. Since Latin was the language of scholarly endeavor at the time, the names were typically in Latin (or Greek made to sound Latin-y) and that served everybody well, since Latin was a dead language and therefore had no "common" names of its own.
In 1735 Carl Linne, a Swedish scientist, decided that another improvement could be made - the names could be made descriptive, such that an organism's scientific name would also include information about how it might be grouped with other organisms, since even by then scientists were seeing a pattern of hierarchical similarity between organisms, a pattern reflected in common use - we have living things, and then a kind of living thing called a "plant", and then a kind of plant called a "tree", and then a kind of tree called an "apple tree", and then a kind of apple tree called "Golden delicious." It's hierarchical, each level getting more and more specific.
Linne was so enamored of the system of classification he created that he Latinized his own name and started calling himself "Carolus Linnaeus." We refer to his system of classification that we now use as "Linnaean classification" - kingdom, phylum, class, order, family, genus, and species - and the use of the genus and species classification to refer to specific organisms as "binomial nomenclature" - two names, like Homo sapiens. In fact, it was Carolus Linnaeus who first provided a scientific name for human beings, and in so doing, made the origin of man a question for scientific research.
Well, ok. So now we have the system by which we name organisms. But when you name an organism, which organisms are you naming? Even just looking at Homo sapiens, that designation refers to a large number of beings who are all very different from each other - men are different than women, white people are different than black people, and so on. Does Homo sapiens refer to all of those different shapes and sizes of people? In other words - what is a species?
This is a question that is not nearly as simple as it sounds, since organisms don't come labeled - there's no part of the human body that you can look at and it says "One ANSI-standard female human being, serial no. 2345-234B." We have to group organisms according to similarity, but not too strictly, or else every single individual is its own species and we've defeated the very notion of classification.
What is a species, then? Scientists have largely settled on a definition that if two organisms are part of the same "reproductive population" - they can either breed with each other, or both breed with a third organism if given the opportunity - then we say they're part of the same species. Unfortunately that doesn't work very well for asexual organisms since they don't breed with anyone. Microbiologists have their own rules about what counts as a species but it's mostly an arbitrary amount of genetic difference.
So today we group organisms into a species, which are all the organisms that can breed with each other, and then group species into a genus, which are all the species that are most similar to each other. We group genera (plural of genus) into families, which are all the genera most similar to each other. We group families into orders, orders into classes, classes into phyla (plural of phylum), and finally phyla into kingdoms, where organisms are the least similar. Kingdom Animalia vs. Kingdom Plantae vs Kingdom Protista (fungi, yeasts.) And actually there are more kingdoms than that but that's the simple version we teach in high school.
It's important to recognize that this is all just bookkeeping. There are no classifications in nature. Animals and plants don't neatly assort themselves into categories, that's a simplifying system that we impose on the natural world. There's no such thing, physically, as a species or a "kind" because there really is no such thing as a "reproductive community." There's just two organisms involved in reproduction without regard as to who else they could hypothetically be reproducing with. The whole notion of classifying organisms is a theoretical notion. We call a dog a "dog" because it looks like other dogs to us, not because it has some kind of inherent dog-nature that separates it from wolves or cats or bears. It wasn't until the rise of molecular systematics three decades ago that we had any real way to determine similarity between organisms except by looking at them and making decisions about what kinds of similarity were more important than other kinds.

This message is a reply to:
 Message 281 by Chuck77, posted 02-26-2012 6:13 AM Chuck77 has replied

Replies to this message:
 Message 291 by Chuck77, posted 02-27-2012 1:02 AM crashfrog has replied

  
crashfrog
Member (Idle past 1581 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


(3)
Message 287 of 331 (654039)
02-26-2012 10:43 AM
Reply to: Message 271 by Chuck77
02-26-2012 2:57 AM


Re: Same kind different species?
Well, that's a good question. I'm not sure. Maybe the same kind but a different species? On the face of it I would say they were the same kind.
Sure, because you're looking at the adults.
But if you were looking at the juveniles, you would see that flying squirrels are placental mammals (like cats and dogs and humans) and gestate entirely in a uterus, while sugar gliders are marsupial mammals (like playtpuses and kangaroos) and gestate partially inside a uterus and partially inside the mother's abdominal pouch.
That's a pretty big difference, because that seems to be an enormous gulf between different sorts of mammals, both morphologically (that is, in terms of form) and genetically. Even creationists assert that marsupials and placentals are in different kinds. Evolutionists agree that flying squirrels and sugar gliders are as distantly related as any placental mammal is to any marsupial - that these two flying mammals are as dissimilar, in terms of evolutionary ancestry and genetic history, as human beings and kangaroos are.
That's why scientists don't talk about things as "kinds" - that word is just insufficiently specific to fully describe the relationship of these two organisms, or any two organisms. We talk about taxons, which are hierarchical, and allows us to point to the exact "level" of the difference: they're both alive, they're both animals, they're both vertebrates, they both have four legs, they both have fur, warm blood, and milk, making them mammals. But now is where they're different: one is a marsupial (actually a sort of possum), the other is placental.
You can see how that hierarchical system already implies a certain evolutionary history - we're the same, we're the same, we're somewhat the same, we're somewhat less the same, we're very much less the same, we're not very alike at all, we're completely different. Classification by increasingly broad categories of physical similarity is a kind of evolutionary history, because that's how new species evolve from old ones - by becoming increasingly dissimilar from them.

This message is a reply to:
 Message 271 by Chuck77, posted 02-26-2012 2:57 AM Chuck77 has replied

Replies to this message:
 Message 292 by Chuck77, posted 02-27-2012 1:15 AM crashfrog has replied

  
crashfrog
Member (Idle past 1581 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


(2)
Message 301 of 331 (654177)
02-27-2012 3:23 PM
Reply to: Message 291 by Chuck77
02-27-2012 1:02 AM


Re: Taxonomy
How can you tell if they are of the same reproductive population? What do you mean?
Well, that's a good question. We can, of course, only reach that conclusion to a certain degree of certainty - we can't take every rabbit in the forest and try to mate it once with every other rabbit in the forest. If we want to know if the rabbits in East Forest are in the same reproductive community as the rabbits in the West Forest, there are some genetic tests we can do - we can take samples from individuals all over the forest, and see if the rabbits from East Forest are more similar to each other, genetically, than they are to the rabbits from West Forest. If a given allele is as likely to be found in the rabbits in East as in West, then we conclude that's the result of "gene flow" between those two groups, and the way that genes flow is by reproduction. So, we would say they're in the same species.
Like I say, it's a hard problem because animals and plants don't come labeled with their species. That's a classification we impose on the natural world for our own human convenience.
Ok. So winged species in this corner, winged with tail over here, winged with tail beak over here?
Yeah, that's basically it. By the time you get to the species level, it's like "Striate areas on the 9th abdominal segment? Melanotus cribulosus. No striate areas? Melanotus depressus." It seems nit-picky, but these tiny morphological differences really do reflect reproductive isolation between species in the same genera. It's reflected in the genetics.
What do you mean there is no such thing as a "reproductive community"?
Well, are you part of the "human reproductive community" in any real sense? Are your children? (I imagine you hope that they are not.) Even if you have reproduced, would you say that it was with a community? Wasn't it just with a single person for whom you are the only person they reproduced with?
The whole notion of "reproductive community" is a matter of theory, it's about who you could hypothetically reproduce with given the right conditions. You could, most likely, father children on any human woman assuming she was of age and fertile, and that you are, as well. But does that mean that your grandparents aren't human beings anymore, since their fertile days are behind them?
No, of course not. It's about what could theoretically happen, who you could theoretically reproduce with, not who you actually do reproduce with. That's why it's not at all trivial to determine the scope of a reproductive community - it doesn't really exist. It's a model about what is possible, not what is real.
Does that make any sense? Obviously it's not ideal but it's the only thing we've got.
So I could actually say that a we are all of the same kind, different species, subspecies all the way down the line?
Well, it depends. What do you mean by that? Creationists use the word "kinds" to refer to the fact that they believe that the Earth is inhabited by multiple groups of organisms, all with their own separate origin. But in the natural world, it's all but impossible to draw those kinds of sharp distinctions between organisms. Whenever you say that one organism is of one kind, and a second is of another, I can go out into nature and find some organism that very neatly splits that difference right down the middle.
Like the sugar glider and flying squirrel...Do you think they should be in the same classification?
Well, they are. They're both mammals, so they're in the same classification "mammal." But within Mammalia, it's hard to imagine how they could be any more different - one is placental and the other is marsupial. That's the most fundamental difference that exists within the class Mammalia. Actually, strike that - there's the monotremes, the egg-laying mammals. (Did I earlier refer to the platypus as a marsupial? That was a mistake on my part.)
Plants, animals, trees, anything alive is catagorized?
Indeed. It's the obligation and privilege of the one who discovers, describes, and classifies a new, undescribed and unclassified organism to name it.

This message is a reply to:
 Message 291 by Chuck77, posted 02-27-2012 1:02 AM Chuck77 has not replied

  
crashfrog
Member (Idle past 1581 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


(1)
Message 302 of 331 (654178)
02-27-2012 3:38 PM
Reply to: Message 292 by Chuck77
02-27-2012 1:15 AM


Re: Same kind different species?
Yet they look almost exactly the same. How?
It's likely the case that this is "convergent evolution", where two species that live in the same kind of environment are independently pressured to develop the same traits. It's not common, but we do see it. Of course, simply by being mammals, these two organisms have upwards of 90% identical genetics (just as you share 90% of the genes of a mouse) so despite starting from "different kinds", they're already pretty similar to begin with.
Well this is going to hard to define what a kind is then, it seems.
To say the least. This problem - how do you define "kind" in terms of something physical that can be observed or tested for - is where creationism has always run aground. Creationists know what they want it to mean - "one group of organisms specifically created by God" - but it's impossible to reconcile that with the natural world.
Yeah interesting. I get it but at the same time I don't, but I do.
A good friend of mine was once challenged, during his PhD defense in zoology, if he knew what a species was. His reply was "I don't, but every day I go to work as though I do." It's not an act of scientific fraud to talk about species as though we know for certain when two organisms are in the same species, or aren't. Like everything else in science, our knowledge about species is provisional, subject to revision in the light of better evidence, and frequently is revised due to new evidence. My wife is an entomologist, and her whole field was scandalized by the results of an enormous new genetic study that determined evolutionary relationships by sequence similarity on the 16S ribosomal subunit (it's one of the few cellular organelles that all living things have, because it's required for life.) The scandal was that the entire class Insecta was found to have descended from Crustacea, which means that they are crustaceans. It was a big upset; everybody used to believe that Insecta and Crustacea were both classes within the phylum Arthropoda.
The TL;DR version of all this is that figuring out what is what, in the natural world, is not very simple at all.

This message is a reply to:
 Message 292 by Chuck77, posted 02-27-2012 1:15 AM Chuck77 has not replied

  
crashfrog
Member (Idle past 1581 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


(1)
Message 323 of 331 (656127)
03-16-2012 4:26 PM
Reply to: Message 322 by Chuck77
03-16-2012 4:14 PM


I'm either giving the wrong impression here or you're just up to your regular insults by actually suggesting I read "The blind watchmaker" by Richard Dawkins. How bout I grab "the god delusion" while we're at it?
Both of those are good books, and you should read them if for no other reason than to expose yourself to the arguments of those you oppose, giving yourself time to come up with rebuttals before we employ them here.
We've done that with creation/ID sources. Why wouldn't we?

This message is a reply to:
 Message 322 by Chuck77, posted 03-16-2012 4:14 PM Chuck77 has not replied

  
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