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Author Topic:   Is There Any Genetic Or Morphological Criterion For "Kind"?
Quetzal
Member (Idle past 4008 days)
Posts: 3228
Joined: 01-09-2002


Message 6 of 40 (352338)
09-26-2006 8:52 AM
Reply to: Message 5 by Faith
09-26-2006 6:27 AM


Expect it eventually will be defined genetically. But meanwhile I liked kuresu's list of hybrids which seemed to fit with what MJFloresta said about how a kind would be determined by ability to interbreed, even if that had to be tested artificially. I wasn't sure about this because I know there are cases where speciation has occurred and interbreeding ability has been lost though the new breed is certainly of the same kind.

The problem is that the two parts of this definition of "kind" appear mutually contradictory. I can sort of accept the "ability to interbreed", which is close to the biological species concept. Even though the "kind" definition stretches it a bit to include artificial breeding, it's not that far off (and certainly would be one way of showing that the two organisms are related, even if the F1's are sterile). However, adding in the part about "certainly the same 'kind'" even though reproductively isolated leaves us back in the same place, without a usable definition. "'Kind' = ability to interbreed except when they can't" isn't very useful.

I'd also like your opinion concerning the second part of the question: how do you determine whether two fossils are the same "kind"? Obviously, an interbreeding test isn't going to work. So what's the criteria?


This message is a reply to:
 Message 5 by Faith, posted 09-26-2006 6:27 AM Faith has responded

Replies to this message:
 Message 7 by mjfloresta, posted 09-26-2006 11:37 AM Quetzal has responded
 Message 18 by Faith, posted 09-27-2006 12:18 AM Quetzal has responded

  
Quetzal
Member (Idle past 4008 days)
Posts: 3228
Joined: 01-09-2002


Message 9 of 40 (352393)
09-26-2006 12:37 PM
Reply to: Message 7 by mjfloresta
09-26-2006 11:37 AM


MJFloresta writes:

My definition for the Kind, as I have oft pointed out, is that individuals of the same kind CAN produce offspring, not that they necessarily will in nature. The issue here is genetics - the actual ability of organisms to produce offspring - not behavior, which may determine whether two organisms in nature [i]will[/w] produce offspring, but say nothing about whether they can or can't.

So what? I already noted that, even though you're stretching the BSC a bit, this was a reasonable definition. Until, of course, you get to the part where two obviously related species can't interbreed, even artificially. Why don't you try actually answering/responding to the post made, rather than simply re-asserting your original point? Try this:

Quetzal writes:

"'Kind' = ability to interbreed except when they can't" isn't very useful.

Faith's contention is that there is some way to objectively identify "kind" even in the absence of the interbreeding criteria.

After you finish that, you can address the second part of the question, which dealt with how a creationist determines whether two fossil organisms are the same "kind".

Edited by Quetzal, : wrong attribution


This message is a reply to:
 Message 7 by mjfloresta, posted 09-26-2006 11:37 AM mjfloresta has not yet responded

Replies to this message:
 Message 10 by MangyTiger, posted 09-26-2006 3:57 PM Quetzal has responded

  
Quetzal
Member (Idle past 4008 days)
Posts: 3228
Joined: 01-09-2002


Message 11 of 40 (352442)
09-26-2006 5:24 PM
Reply to: Message 10 by MangyTiger
09-26-2006 3:57 PM


Re: Mistaken identity
You're absolutely right. I've fixed it. Bizarre brain burp there...
This message is a reply to:
 Message 10 by MangyTiger, posted 09-26-2006 3:57 PM MangyTiger has not yet responded

  
Quetzal
Member (Idle past 4008 days)
Posts: 3228
Joined: 01-09-2002


Message 21 of 40 (352620)
09-27-2006 11:58 AM
Reply to: Message 18 by Faith
09-27-2006 12:18 AM


I know. I should not have added my doubtful thought at the end, which contradicted the first part as you say. Just because they don't doesn't mean they can't. The fact that many don't proves nothing in other words.

Well, if you mean "don't in the wild", then you're right - it doesn't prove much. It also doesn't help the definition of "kind" we're trying to reach. MJFloresta insists that the interbreeding criteria is the sole determinant. As you pointed out, that doesn't always work - there are a lot of organisms that are superficially similar (you mentioned a morphological criteria as the "fall back" - which of course ran us smack into the reproductive wall contradiction you recognize here) that simply can't interbreed, regardless of circumstances. Not "don't want to", but actually can't produce fertile hybrids (see next).

I was thinking of a frog species somebody posted about on another forum a long time ago, and I don't remember its name, but it's a member of the frog kind and there is no doubt, not something new. HOw do I know? I don't know. It's just obvious.

This brings to mind an example that might be illustrative of the problem any definition of "kind" needs to overcome. Remember this little cutie?


Click to enlarge
It is a glass frog of the family Centrolenidae, which includes glass frogs and leaf frogs, that we found in the reserve I'm working in. Clearly, it is "frog kind". Morphologically (at least superficially), they resemble the Hylidae, or tree frogs, as many of the latter are small, green, and dwell in the canopy like the Centrolenidae in Ecuador. They even sound, to the untrained ear, like each other (they're both peepers). However, the details of their morphology (they have multiple different structures, even different organs), behavior, genetics, etc, make it literally impossible for them to mate - even artificially: the chromosomes don't line up properly* - they are not interfertile by any stretch. Your "I just know it" definition of "kind" - an objectively useless distinction - is the only way these two families can be considered the same. Genetically, reproductively, morphologically, behaviorally, and even in terms of ecological role, parental care, egg-laying strategies, etc, they are very different groups of organisms. Where can you draw the "kind" line?

I'm tempted to say that whatever most people would be inclined to call the thing (at least in most cases -- there would always be exceptions) is probably close to a definition of the Kind.

Unfortunately, "whatever most people would be inclined to call the thing" doesn't provide any real possibility of distinguishing one group of organisms from another. For example, what is an "elk"? The common name “elk” (what most people are inclined to call the thing) describes very different organisms in Europe and North America, even though the term is used in both places. A European “elk” is called a moose in North America, whereas the North American “elk” is referred to by Europeans as a “red deer”. Add in recently vanished organisms such as the “Irish Elk” – a type of fallow deer – and anyone attempting to communicate any kind of useful information about the critter is completely at sea, awash in conflicting nomenclature. Common names are pretty worthless outside of really obvious things like "dog", "cat", "sheep", etc. Even here, the differences between what scientists call Felis catus, and say Puma concolor or Leopardis pardalis render "cat" a fairly worthless piece of nomenclature from any practical standpoint. This is pretty much the entire reason why Linnaeus came up with the binomial nomenclature in the first place. If you're going to replace this with "kind" - for whatever reason - it's got to be at least as useful and operationally defined as what is now in use. Until you (generically speaking - I'm aware you personally don't have more than a vague idea on the subject), can do this, I see no reason for anyone to take the "kind" term seriously.

Someday it will have to be genetically defined. Or maybe Jesus will come back first.

If I were you, I'd bet on the latter, since genetics not only doesn't support the concept, but quite clearly refutes its existence.

*Before you ask - no, no one has attempted to perform this experiment. Why would they? The chromosomes are so different, the arrangement of functional genes so different, that there is clearly no way for it to work. Eggs from the one simply physically can't be fertilized by sperm from the other.


This message is a reply to:
 Message 18 by Faith, posted 09-27-2006 12:18 AM Faith has not yet responded

  
Quetzal
Member (Idle past 4008 days)
Posts: 3228
Joined: 01-09-2002


Message 22 of 40 (353099)
09-29-2006 10:15 AM


Bumpity Bump for Faith
I know you have a lot of threads you are currently involved with, but I would appreciate your reply to my previous (post #21).
  
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