Evolution Question-Interspecies Breeding

[MostlyHarmless]

I am a lapsed forum member, I have not visited for several months. Even then I mostly kept to the shadows and just observed.

Now I find that I have a question which I hope the forum can answer:

Are there any instances in nature where animal type A can breed with animal type B, and animal type B can breed with animal type C, but A cannot breed with C? I refer to viable offspring only.

It seems to me that if there is such a case it would present a relationship between species that creationists would find uncomfortable.

I could not figure out a productive way to search for entries on this. If it has been covered before, I throw myself on the mercy of the forum.

 

[Jeff Corey]

Don't know, but there is a start. If you mean "type" to be species, lions and tigers have interbred, but not willingly.
But I don't know if either of those have been crossed with other cats.
And I can't see how if species A, B and C could or couldn't all interbreed would settle a question.
What is the question?

 

[SpaceFluffer]

I know that Zebra's can mate with Donkeys, and Donkeys can mate with Horses. But I'm not sure if Zebra's can mate with horses or not.

Why would this cause creationists to be uncomfortable?

 

[MostlyHarmless]

Biology was never my strong suit, and maybe I am barking up the wrong tree, but please bear with me. Any comments pro or con are of course welcome.

I have often heard creationists say that macroevolution is possible, but microevolution is a fantasy(or do I have the terms backward). Species are often defined as animals which can breed and produce viable young.

Although I know that this is not the only definition of species, it seems to me that proving a kind of chain of breeding ability without "inter-species breeding" could show an inter-relatedness that creationists deny.

Imagine that homo sapiens could be proven able to bread with neanderthals, and neanderthals could be proven able to breed with "proto chimpanzees". Pardon my non-scientific jargon, I do not claim to be scientifically educated.

 

[Floyt]

Yup! This is in fact a well-established phenomenon. Species were it occurs are called ring species, from the first observed example (Herring gulls) that forms a disjunct interbreeding circle round the North Pole. Go here for some details.

 

[MostlyHarmless]

Floyt:

Thanks for the link, that is really cool. I wasn't sure if this would occur in living animals.

 

[Gwyn ap Nudd]

Unfortunately, if you were hoping to use this example to "prove" macroevolution (speciation), the fundies still won't buy it.

For too long, they have heard arguments about the size of Noah's Ark and about tiglons and ligers and mules (Oh my!). They are often ready to drop the distinction between "micro-evolution" and "macro-evolution" back from "species" to "kind," where kind is a vague level of taxonomy somewhere between "kingdom" and "species." By not identifying "kind" with any specific taxonomic level it saves face as they find themselves forced to back-pedal through the levels

In other words, Noah might not have brought (for example) two Siberian tigers, two Bengal tigers, etc. He might not even have brought two (generic) tigers and two (generic) lions, but only one pair of generic "big cat," or even possibly one pair of felines. Likewise, he need not have brought horses, donkeys, zebras, etc, but merely one pair of "equines." And only one "kind" of canine, etc. But a tiger could never descend from a canine, or a wolf from a feline. (Trivially true, but both could descend from an earlier species, except they would have have had to have diverged long before the Creationists' date for the beginning of the world.)

 

[MostlyHarmless]

Gwyn ap Nudd:

It goes without saying that you are correct about the fundies, but there are many(a suprising number) who are swayed by their rhetoric, who may only need a small justification to change their minds.

I do not consider myself a great debunker of irrational thought, but I work in an area where I can influence a small number of young adults in a limited way. If I can put some doubt in the minds of these young people about beliefs which have no evidence to support them, I feel that I have gained an incremental victory for rational thought.

 

[Mojo]

In other words, Noah might not have brought (for example) two Siberian tigers, two Bengal tigers, etc. He might not even have brought two (generic) tigers and two (generic) lions, but only one pair of generic "big cat," or even possibly one pair of felines. Likewise, he need not have brought horses, donkeys, zebras, etc, but merely one pair of "equines." And only one "kind" of canine, etc. But a tiger could never descend from a canine, or a wolf from a feline. (Trivially true, but both could descend from an earlier species, except they would have have had to have diverged long before the Creationists' date for the beginning of the world.)

A few months ago I asked Nick Harman, a visiting fundie, how all the existing species can have arisen from a limited number of "kinds" without evolution (i.e. one species arising from another) taking place. I don't think I got a coherent answer.

 

[clarsct]

You expected a coherent answer from a YEC?


Huh. Optimistic sort, aren't you?

 

[athon]

The concept of 'species' always muddies the water. It's inadequate to explain the spectrum of genetic differences. Unfortunately, right now it's the best system we have to be able to classify.

To think that it is so subjective as to where one can draw a line of distinction between two genotypes. The traditional definition of species, for instance, relies on enough genetic differences to prevent any potential resulting offspring from being viable. This is not necessarily a percentage of genetic incompatibility, but also of particular genes that are incompatible.

I don't think there'll ever be a catch-phrase or answer that will satisfy hardcore fundies. But sometimes I wonder if we'll ever change classification systems to reflect nature a little better.

Athon

 

[Mojo]

You expected a coherent answer from a YEC?

Well, not really. But at least it got amusing thereafter, as his attempt to answer it involved introducing ring species into the discussion.

 

[Rolfe]

This may sound weird coming from someone who regularly squares up to homoeopaths, but is there really any point in trying to engage in rational discussion with someone who maintains that the Noah's ark story is literally true?

Rolfe.

 

[Mojo]

This may sound weird coming from someone who regularly squares up to homoeopaths, but is there really any point in trying to engage in rational discussion with someone who maintains that the Noah's ark story is literally true?

About as much point as there is in trying to explain anything to Kumar, I suppose...

 

[toddjh]

I've found that you can make creationists very uncomfortable by pinning them down on what exactly constitutes micro- versus macroevolution.

For example, they are very big on "kinds," and often say that microevolution is allowed within a "kind" (horses, donkeys, zebras, etc.) even though you'll never see one "kind" giving birth to another.

The problem comes because they are forced by their theology to declare that humans and apes are necessarily two different "kinds," despite the fact that we are extremely similar genetically. In fact, humans and apes are more closely related than lots of other animals which the creationists happily consider the same "kind."

For this reason, the creationist is forced to either concede that humans evolving from earlier primates counts as microevolution, or else invoke a supernatural explanation that mankind is "special" and, unlike other animals, our genetic similarity to other apes does not imply common descent. No bets on which they'll choose, but it does seriously undermine their claim that "intelligent design" is based on science and not religion.

Jeremy

 

[drkitten]

I am a lapsed forum member, I have not visited for several months. Even then I mostly kept to the shadows and just observed.

Now I find that I have a question which I hope the forum can answer:

Are there any instances in nature where animal type A can breed with animal type B, and animal type B can breed with animal type C, but A cannot breed with C? I refer to viable offspring only.

In answer to the original post, yes, there are instances. The term for which you might want to search the web is "ring species." Basically, they're situations where animal subtypes that do not naturally interbreed among themselves.

This page describes (briefly) two of the better-known examples of ring species. Dawkins goes into this in some detail in his recent book The Ancestor's Tale; look for this discussion under the heading "The Salamander's Tale."

 

[CBL4]

Gwyn ap Nudd,

This type of YEC creationist argument leads to some very interesting ideas. It means that all the big cats (micro)evolved from a common stock in less than 6000 years! Each decade we should several newly evolved species of cats, deers, equine, etc. It is very interesting that such rapid evolution suddenly stopped in the last few centuries.

BTW, the goal should not be to convert the hard core creationists. That is impossible. The goal should be to convince the average person that the creationists are idiots. To be effective, it needs to be done nicely of course.

CBL

 

[fishbob]

The concept of 'species' always muddies the water.

Side track: Interesting choice of words, when in discussion with Mojo.

 

[MostlyHarmless]

Thanks new drkitten, another good link.

toddjh: What you are saying was pretty much my point in starting this post. If you could show that two "kinds" which don't interbreed share an animal with which they both breed (not necessarily at the same time ), it seems to me that these kinds are not so distinct as the creationists would like.

I have no illusions of converting a true fundie, but any ammo I can get to use when talking to fence sitters is welcome.

 

[davefoc]

What an interesting notion. I had no idea that ring species existed. Thanks for the links. And thanks to new drkitten who never ceases to surprise me with the range of her knowledge.

As to the Noah's ark thing, I think some of the Noah's ark threads have been the most entertaining in the history of the JREF forum. The whole idea just makes me smile a little thinking about it. One of the things I would note is that there seems to be at least two kinds of folks who believe in Noah's ark, the absolute literalists and the apologists.

The absolute literalists are by far the most fun. They have some specific ideas and don't allow any amount of common sense to stand in their way. The apologists are much less fun. They have lots of esoteric theories about how something in the original story might be correct but when you get down to it, the problem the apologists have is that if you just deviate from the literal story whenever required to make it remotely plausible then there doesn't seem to be much reason to assign what remains of the biblical story any credibility.