How exactly does speciation occur according to Evolution theory?

[Fanghur]

A little while ago my uncle and I were discussing the theory of evolution and the appalling percentage of Americans (I'm Canadian, by the way) who still don't believe in evolution. I had made the claim that even though the theory may very well be incomplete, evolution is a proven phenomenon, which it is. And he made a point that I found interesting, and that was that the theory is indeed incomplete because we still are not able to explain how speciation occurs using the theory. The example he used was that even though humans have been breeding animals like dogs, cats, etc. for thousands of years, and artificially selecting for certain traits that we find appealing for one reason or another, which is effectively what evolution does naturally albeit at a hugely accelerated rate since we are able to specifically breed dog X with dog Y in order to get trait Z, which if left to natural evolution might take thousands or even millions of years to occur.

 

And that even though we have effectively been carrying out artificial evolution on animals at hugely accelerated rates for thousands of years, we have still been as yet unable to produce any actual new species by doing it. That is to say, for example, even though Chihuahuas and Great Danes look vastly different in every way due to our breeding, they are still technically the same species, because they could theoretically interbreed to produce fertile offspring (notwithstanding the fact that would probably be fatal if the Chihuahua was the female), and we have not yet succeeded in actually producing any new species of dog, as the definition of species stands.

 

That was just one example of what my uncle was trying to point out, he didn't just base his entire argument on that. He concluded that while the Theory of Evolution is indeed accurate, and I know for a fact that it is, it currently fails to adequately explain how speciation occurs. And I must say, I did find his argument compelling. Can anyone explain if it has any flaws, and if so, what they are?

 

And just to be perfectly clear, I am trying to better my understanding of Evolution, not pick holes in the theory.

[Arete]

Speciation has indeed been observed: have a read through here for a comprehensive explanation and a number of examples

 

http://www.talkorigins.org/faqs/faq-speciation.html

[Ringer]

It explains how speciation occurs. A speciation event is when an ancestral species becomes a single, or multiple, new species. Ways this can happen are very numerous, but basically two groups of the same species are isolated, geographically or because of niche, and no longer interbreed. Since they no longer interbreed each population will end up generating different mutations throughout generations. When enough of these mutations compound the two populations can no longer interbreed to produce viable offspring.

 

 

There are also different meanings for species that work for some organisms and don't work for others. Biology likes to make a crap-shoot of trying to categorize things, so most of the time there will be an example that gets brought up that won't work for things like my explanation, like those damn asexual organisms.

[Moontanman]

A little while ago my uncle and I were discussing the theory of evolution and the appalling percentage of Americans (I'm Canadian, by the way) who still don't believe in evolution. I had made the claim that even though the theory may very well be incomplete, evolution is a proven phenomenon, which it is. And he made a point that I found interesting, and that was that the theory is indeed incomplete because we still are not able to explain how speciation occurs using the theory.

 

We can indeed explain how speciation occurs, this is a strawman...

 

 

The example he used was that even though humans have been breeding animals like dogs, cats, etc. for thousands of years, and artificially selecting for certain traits that we find appealing for one reason or another, which is effectively what evolution does naturally albeit at a hugely accelerated rate since we are able to specifically breed dog X with dog Y in order to get trait Z, which if left to natural evolution might take thousands or even millions of years to occur.

 

This part is true, we do indeed make new breeds of animals via artificial selection.

 

And that even though we have effectively been carrying out artificial evolution on animals at hugely accelerated rates for thousands of years, we have still been as yet unable to produce any actual new species by doing it. That is to say, for example, even though Chihuahuas and Great Danes look vastly different in every way due to our breeding, they are still technically the same species, because they could theoretically interbreed to produce fertile offspring (notwithstanding the fact that would probably be fatal if the Chihuahua was the female), and we have not yet succeeded in actually producing any new species of dog, as the definition of species stands.

 

This is a bit misleading, if you had an isolated population of chihuahuas and Great Danes they could not reproduce and would satisfy the requirements of being separate species. many species can reproduce with other but do not do so due to environmental factors such as isolation. Dogs in my opinion are more like ring species, we have simply breed so many grades of dogs that they all seem to be able to reproduce but as you suggested some are not compatible with others but in effect they all are compatible with at least some of the different breeds.

 

Different species can be the result of geographic isolation as well as simply being physically impossible for the two species to mate, it does not necessarily mean they cannot be cross fertile. We can and do mate different species in captivity and in rare cases they can be fertile and cross fertile with the parent species. It would be easy to simply declare Great Danes and Chihuahua different species due to the fact that reproduction is not naturally possible between the species, because we know they were recently the same species and is a result of artificial selection instead of natural selection the idea of simply declaring them different species is not well thought of.

 

There is also the problem of the dog genome being so plastic that left to natural forces most dogs will over time revert to a less "artificially selected" form, if say for instance Chihuahuas were left on some island isolated with no humans to select their form they would not be Chihuahuas after many generations... no artificially selected dog breed would breed true in the wild removed from the pressure of selection by humans... since the selection pressure is artificial and not natural by definition the idea of species is blurred in these and other domestic animals... I think it is safe to say that few people would mistake a domestic cow for an auroch or a mouflon for a domestic sheep.

 

That was just one example of what my uncle was trying to point out, he didn't just base his entire argument on that. He concluded that while the Theory of Evolution is indeed accurate, and I know for a fact that it is, it currently fails to adequately explain how speciation occurs. And I must say, I did find his argument compelling. Can anyone explain if it has any flaws, and if so, what they are?

 

And just to be perfectly clear, I am trying to better my understanding of Evolution, not pick holes in the theory.

 

 

Again, that is a strawman argument since indeed we do know how speciation occurs.

 

http://en.wikipedia.org/wiki/Speciation

Edited July 14, 2012 by Moontanman