Thread: A question regarding speciation as described by the Theory of Evolution?

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 (I'm talking about in animals here, not bacteria, as they have slightly different definitions of species). 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 it 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.

Yes! Yet another chance to link to one of my favourite online resources ever.

Ring species -- the abridged version - YouTube

The rest of Potholer's evolution series is pretty good. But not always recommended for the thin-skinned fundamentalist. Use the 'schools' versions for anyone who's likely to faint away under an onslaught of snark and ridicule.

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

If something killed all the canids except Great Danes and Chihuahuas, there would be two different species of dog on the planet.

Just as there is maize and several other plants that need only genetic isolation and selection against the intermediaries to be species of their own, bred by humans from wild plants.

Nature kills off the intermediaries, in nature physical barriers prevent genetic mixing for long enough, etc etc. That's the only difference - otherwise humans have demonstrated evolution in their breeding efforts quite persuasively.

Originally Posted by Fanghur

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 it 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.

A couple of points on this example. Firstly, the idea of "species" is a purely human one and has no clear definition (people arguing from a creationist perspective seem to think it is based on some sort of Natural Law). The one you give is commonly used but it cannot always be applied. Also, the inability to interbreed does not just have to be down to genetic incompatibility. For example, there are groups of animals which are geographically separated but counted as two species even though the would happily interbreed if put together.

Also, you say that the Great Dane and Chihuahua could successfully interbreed (in a lab environment) and yet it might be fatal for one of them. That is a very limited definition of "success"

Many new species and varieties have been produced by hybridization: cross-breeding things which are different species. This is most common in plants.

Related to this, we have domesticated crops for far longer than dogs and have indisputably produced new species in this way.

This page gives a good description of the problem of defining species and examples of new species being observed:
Observed Instances of Speciation

Yep.. look at the carrot.. We made it orange... it's normally purple or white..

Fanghur's uncle does, however, have an interesting point with historical resonance. The one thing that On the Origin of Species does not do is give a good explanation of the origin of species. Rather it gives an excellent explanation of how certain traits that arise from natural variation can be selected for, naturally. That is subtly different from demonstrating the origin of a new species.

it was also clear from his barnacle work that Darwin was having serious problems with how to define a species

Originally Posted by marnixR

it was also clear from his barnacle work that Darwin was having serious problems with how to define a species

And I speculate that this was because he was still unduly influenced by the concept that species were real things rather than an artifact of human classification.

Hmm.. In that case, we have to throw all the textbooks out of the window because a species would not be defined by us.. but by.. whom?? If we don't who will?

Agreed, "species" is a fluid term. If we define species by morphology, that is physical shape and function, rather than ablity to have fertile offspring it becomes less fluid.
Defined this way a chihuahua is a different species from a dane.

Also remember that evolution is driven by death. The poster who stated that the intermediates need to be killed off to define the different daughter species from the parent one, was right.

Originally Posted by Zwolver

Hmm.. In that case, we have to throw all the textbooks out of the window because a species would not be defined by us..

What?! The central point is that species are defined by us, for our convenience, but that such definition is ultimately artificial. This is hardly a matter for dispute.

Originally Posted by John Galt

Originally Posted by Zwolver

Hmm.. In that case, we have to throw all the textbooks out of the window because a species would not be defined by us..

What?! The central point is that species are defined by us, for our convenience, but that such definition is ultimately artificial. This is hardly a matter for dispute.

which does not mean that they don't have some sort of reality attached to them, it merely means that a species is fuzzy at the edges
otherwise you'd be arguing that the colours black and white don't exist because of the shades of grey inbetween

Originally Posted by marnixR

Originally Posted by John Galt

Originally Posted by Zwolver

Hmm.. In that case, we have to throw all the textbooks out of the window because a species would not be defined by us..

What?! The central point is that species are defined by us, for our convenience, but that such definition is ultimately artificial. This is hardly a matter for dispute.

which does not mean that they don't have some sort of reality attached to them, it merely means that a species is fuzzy at the edges
otherwise you'd be arguing that the colours black and white don't exist because of the shades of grey inbetween

Which would be silly. A frog is clearly not a horse, but less clearly not a toad. The point is that there is not clear dividing line.