What is the definition of a species? At what point (biologically, taxonomically?) does an individual cross a line and move from one species to form a new one? Is it based on the ability to breed?
Imagine the following situation.
Generation 0: a group of mice, say, are on an island. They are spread all over the island.
At Generation N, a natural catastophe occurs, and splits the island in two.
Generation N + 1: presumably, the two separate groups are still the same species (and can interbreed).
One group diverges (sharper teeth? longer legs?). But they can still interbreed.
Generation M: still the same species.
Generation M + 1: hey, theycan’t interbreed! Do we say that the new species starts here?
I think there are two basic approaches to defining a species. Taxonomists define a species as groups of animals with particular characteristics. Geneticists, on the other hand, will define a species in terms of whether or not its members can interbreed.
Taxonomists are known to argue endlessly about what characteristics are important, and where the lines should be drawn. The genetic definition isn’t quite as arbitrary, but it is not always useful. For example, it doesn’t address the issue of organisms that reproduce asexually.
the concept of species is weak, and only survives for historical reasons, and because its intuitively descriptive. there is no such thing as species, in fact, just as there is no such thing as flogiston.
I wouldn’t go that far, zeno. The concept of “species” is very useful. Imagine trying to describe or understand a musical composition without referring to specific harmonic structures. One’s definition of the structure of a particular musical scale may be arbitrary, but it is very useful. Similarly, while our definition of a particular species may be arbitrary, it is practically impossible to describe or understand evolution and the complexity of life without it.
The example of flogiston is not fair, either. It’s not like “species” is defined as a particular substance. It’s a category, and it is defined in terms of observable phenomena. Scientists can test to see whether or not a particular organisms is of a particular species. This is true regardless of the fact that one’s criteria is arbitrary.
i never said its not usefull. its usefull. but its still weak. just like the concept of “empty bottle” is usefull, but weak.
and while the definition might be arbitrary, that was never my objection. my objection was that the definition wasnt formal, and most likely cant be formalised, at least not maintaining any value.
and while the example of flogiston isnt fair, your view that scientists can test to establish species is wrong. scientists can do two things, they can do genetic testing to see dna similarities wich end up in “some sort of this or the other” and taxonomic comparison, which end up in “some sort of this or the other”. but since there doesnt exist a “deer of all deers” the very notion of using cathegories is on a weak footing. what do you compare to ? averages ? so species change each generation. historical averages ? arbitrary definitions ? so species change with each point of view.
species dont exist, the word does not denote a real situation, just as god doesnt exist. you can hop up and down explaining how usefull it is as a concept, but that wont help much.
What I said was that scientists can test to see if a particular organism is a member of a particular species. In other words, a scientist can look at your blood, for example, and tell that you are a human being, and not, say, a rat.
If you think there is something wrong with scientists calling you a human being, and not a rat, you’ll have to explain yourself. These seem like descriptions based on solid, repeatable observations.
There are deers. They are observably different from snakes. Do you doubt this?
This is only evidence that any particular definition of a particular species is arbitrary. That doesn’t make it unscientific, nor does it mean that species don’t actually exist.
Let’s look at the music analogy again to drive the point home. We can break up the tones in a musical scale any number of different ways. We arbitrarily decide to call one particular tone the “root,” and from there come to define other tones as “fourth,” “fifth” and so on. This is arbitrary. Would you conclude, therefore, that musical scales don’t exist? Or would you conclude that our approach to musical scales is arbitrary, yet a practical way of discussing the way things are actually organized?
Do I look like I’m hopping up and down?
Anyway, the comparison to the idea of god is even less fair than your previous example of flogiston. The term “god” is not defined in any way which allows for tests against observations. In fact, generally speaking, it is defined in such a way so that it cannot be described with any reference to observable phenomena. The notion of “species,” on the other hand, is defined with reference to observable phenomena. It is a scientific concept, and can be discussed rationally as such.
If it were true that all organisms were of the exact same type–they all have the same behavioral characteristics, they all can interbreed, and they all share the same niche–then observations could demonstrate that there is only one species, and not many. As it is, observable differences do exist, and we can refer to different sets of organisms using the term “species.”
At the 30,000 foot overview level of seeing things species can be helpful. A snake is clearly different from a rat, is clearly different from a deer is clearly different from a human. What about when you get into the nitty-gritty? What about different kinds of snakes or different kinds of deer?
I could be wrong, but I think that was the level that zenofeller was addressing. That is the level where the usefulness of the term species hits the point of diminishing returns. Differences at that level are slight. Boundaries are difficult to discern.
There are certainly marginal cases where organisms are hard to classify. However, that is not evidence that species don’t exist. It is only evidence that the process of classification is arbitrary and not always useful.
Maybe in appearance, though sometimes, that is arguable too haha. However, there is always that economics based description of most living organisms. Thus, in some instances, I fail to see differences when behaviour can be explained by understanding the organism is merely trying to delay its destruction. Still, I do believe (or maybe foolishly hope) that there is inconsistency in moving from paper (or screen) to experience.
pragmatist, you cant at the same time say about something that is arbitrary and it exists. if its arbitrary it doesnt exist. if it exists its not arbitrary. something cant arbitrarily exist, unless you are god, and your will makes existance.
about looking at my blood, suppose i provide you with a sample of my blood and ask you : is this a cimpanzee, a human, or the missing link ? what will you say then ? they are not based on solid, or repeatable observation. they are based on arbitrarity and conjecture. usefull they might be, but real they are not.
i do not doubt there are deers. i do not doubt you can differentiate any given deer from any given snake. but there is no deer that is a model for all other deers, to which we can compare them. hence, there is no real cause for the cathegory. nails come in types. if we have some 12 inch nails, there is a perfect cause for us to consider them in the same cathegory : the comparison with the ideal 12 inch nail, which is their model. there is no such thing about living beings.
stop bothering yourself with deer and snakes, and think viruses and bacteria. which is a mutated individual part of a species, and which is a new species ?
"This is only evidence that any particular definition of a particular species is arbitrary. That doesn’t make it unscientific, nor does it mean that species don’t actually exist. "
it doesnt make it unscientific, at least inasmuch as its not abused. but it does mean species dont actually exist.
music scales dont actually exist either, wether they are practical or not.
god is very frequently described with plenty of relationship to observable phenomena. christians call them miracles. locals around here are in a huf because they just got their hands on some hubble photo that looks somewhat like a rose, and they have a qu’ran verset saying something like “and when allah makes the skies look like a rose, which of the blessings of the prohphet will you then [still] deny”
so the difference you find between the notion of “species” and the notion of “god” doesnt hold water. care to try again ?
What I said was the the term “species” may be arbitrarily defined; the referent, however, is what exists. The referent is not arbitrary. Rather, the referent is a set of actual organisms. They exist.
The referent is not some Platonic Ideal. The species “deer” is not based on some Platonic notion of Deerness. It is based on observations and measurements of extant organisms.
I’ll say, “I’m not qualified to give you a scientific answer and, please, try not to get any of that on me.”
Mental note: zeno willfully disregards scientific evidence when it suits his argument.
The fallacy in your reasoning is as follows: you assume that one must have a tangible ideal in order to establish a “real cause” for a category. At the same time, you recognize that we can observe differences between deers and snakes. Therefore, you accept that the terms “deer” and “snake” are categories based on observations. One must conclude that there is a “real cause” for the categories of “snake” and “deer,” and that one does not need a tangible ideal in order to establish a “real cause” for a category. The contradiction is evident.
How accurately is your “ideal 12-inch nail” measured? Must we use an electron microscope to come up with a nail as close as possible to 12 inches? Even then, quantum indeterminacy will make it impossible to perfectly measure the length of your “ideal 12-inch nail.” Must we now conclude that there is no “real cause” for the “12-inch nail” category? Must we, in fact, announce to hardwarde manufacturers that “12-inch nails” do not exist?
It depends on the mutation. If you’d like to discuss a specific case, you’ll have to be more specific.
So, something can be practical, and yet not exist. Is that it? If something is practical, it can be used. If it can be used, it exists. Again, the contradiction in your position is evident.
People may refer to observable phenomena as “miracles” which are supposed to point to God’s existence. This is not scientific, because there is no definition of “God” which allows for a test against empirical experimentation.
Again, the definition of God is not made with reference to observable phenomena. In other words, while some people may base their belief on observable phenomena, doing so is not rational. There is no criterion of measurement which grounds the term “God” in observable phenomena.
The difference is apparent. You simply failed to grasp it.
I once asked my professor why we divide wildlife into sub-species and not man. He said they are split if they won’t mix. He went further to say they are able to mix but they choose not to. For example there are 250 different sub-species of sparrows and although they may differ in the slightest way they won’t mix. It is a law of Nature. Creatures split and develop unique adaptations, and in staying separate they evolve. If they mix they end up loosing their unique adaptations.
E.g. Michael Jordan. What would he of been had he had my mother? Well he wouldn’t of had the Power that Nature gave him because his father would of broken a law that all of Nature follows. Only domesticated sick creatures break this law or creatures in captivity.
Either your teacher was confused, or you confused the facts. There is no natural law that says sub-species cannot, or should not, interbreed. Your racist implication (that there is something sick about people of different races interbreeding) is even further removed from any legitimate scientific theory.
Pragmatist.
I challenge you to find me an example of an undomesticated bird, insect, or mammal that mixes. There have been unique cases where organism close to extiction will mix, but that is it. There are about 250 different sub-species of sparrow, but they will not mix. They may live in the same environment but they do not commit this crime. All of Nature speaks Truth, what can the modern human-animal say against all of nature?
~Truth~
If you both accept that then Truth is correct (Man does not breed with Equines, and subspecies don’t mix), and Pragmatist is right in that there is no problem with Asians and Blacks, etc.
Is that the end of the argument? (By the way, it is my thread!)
