Speciation? (Darwin, evolution, science, Article)

[tomspug]

The dogs example isn't a good one. The variations of dog breeds is in their genetics. It's not an example of evolution at all. They're all the same species, even though they can look so unique. Although it's an excellent demonstration of the variety of a single genetic code.

[Seyorni]

But continue the selective breeding long enough, and you'll have a new species.

[rojse]

Originally Posted by tomspug

The dogs example isn't a good one. The variations of dog breeds is in their genetics. It's not an example of evolution at all. They're all the same species, even though they can look so unique. Although it's an excellent demonstration of the variety of a single genetic code.

Surely the fact that not all dogs can breed together shows some speciation?

[MidnightBlue]

Originally Posted by rojse

Surely the fact that not all dogs can breed together shows some speciation?

The reason some breeds can't reproduce is size. The larger breeds and the smaller breeds can both reproduce with intermediate sized breeds.

Reproduction isn't always the test, though. The horse (Equus caballus) can reproduce with the donkey (Equus asinus), although the offspring (mules and hinnies) are almost always sterile. The wolf (Canis lupus) can reproduce not only with the dog (Canis lupus familiaris) and the dingo (Canis lupus dingo), which are descended from the wolf, but also with the coyote (Canis latrans) and the various species of jackal, in each case producing fertile offspring.

[rojse]

Originally Posted by MidnightBlue

The reason some breeds can't reproduce is size. The larger breeds and the smaller breeds can both reproduce with intermediate sized breeds.

It is quite tricky to define a species, (I can't find any official definition) and that's why I went with a rough definition.

If you can give me a good definition, I will work with that.

However, surely the vast difference in size is some evidence of evolutionary mechanics at work?

Originally Posted by MidnightBlue

Reproduction isn't always the test, though. The horse (Equus caballus) can reproduce with the donkey (Equus asinus), although the offspring (mules and hinnies) are almost always sterile. The wolf (Canis lupus) can reproduce not only with the dog (Canis lupus familiaris) and the dingo (Canis lupus dingo), which are descended from the wolf, but also with the coyote (Canis latrans) and the various species of jackal, in each case producing fertile offspring.

I pointed that out in my post, that my definition was only rough, and I explicitly used the horse example.

[fantôme profane]

Originally Posted by MidnightBlue

The reason some breeds can't reproduce is size. The larger breeds and the smaller breeds can both reproduce with intermediate sized breeds.

So if all the intermediary sized breeds were to die out, that would constitute a speciation event.

[logician]

The line between species is a bit hazy, especially in the fossil record. The lion and tiger are separate species, for example, but can interbreed, although the offspring may be able to breed. If one found their fossils much later in the future, they would most likely be assigned to the same species. The problem with fossils is that one only sees the bone structure and not the outward traits of the animal, so assigning species from fossils is more of an educated guess.

[MidnightBlue]

Originally Posted by rojse

It is quite tricky to define a species, (I can't find any official definition) and that's why I went with a rough definition.

If you can give me a good definition, I will work with that.

However, surely the vast difference in size is some evidence of evolutionary mechanics at work?

I pointed that out in my post, that my definition was only rough, and I explicitly used the horse example.

I was just commenting, not disagreeing with you.

One of the reasons defining a species is tricky is that speciation is gradual both in time and geography. I mean, it's not like one day Homo erectus women just started giving birth to Homo sapiens babies. And everything is evolving all the time. Every species we see, including our own, is either an intermediate species on the way to being something else, or a species that's bound for extinction.

[Blentyn chan Celi]

So, we have a consensus that a species is hard to define. I suppose this will pose a problem for the remainder of this discussion because you may cite an experiment where speciation was observed, but I can claim that the two are still one species. With that said, I would like to see them anyway. I am more interested in learning about the theory than arguing about it.

[rojse]

Originally Posted by Blentyn chan Celi

So, we have a consensus that a species is hard to define. I suppose this will pose a problem for the remainder of this discussion because you may cite an experiment where speciation was observed, but I can claim that the two are still one species. With that said, I would like to see them anyway. I am more interested in learning about the theory than arguing about it.

Even though there is some disagreement about the dogs, have you had a look about what I said about viruses? That's a textbook example of evolution.

Aside from that, whenever you hear the phrase "x became resistant to y," that is evolution in action, just shortened for simpler discussion. For example, pests that become resistant to poisons is because the initial bugs that survived the poison were able to breed, and pass their genes on to the next generation. The weeds that could survive spraying were able to spread their seed, while their otherwise identical counterparts died off in the spraying.