Re: Speciation discussion, expectations and reality
I don't know how science can build their models of speciation since humans have directly or indirectly affected the course of natural evolution.
But, of course this was the great insight of Darwin - it doesn't matter. Darwin was observing a breeder of pigeons - watching the breeder select the best-suited individuals from his flock to be mated with each other, and the worst-suited individuals become the sunday roast - when he realized it works the same way in the natural world.
In the natural world, those that are possessed of the adaptations crucial for survival in their environment survive and prosper, and most importantly <I>mate</I>, and those that do not quickly become someone's lunch. It's no different than the selection by the pigeon breeder, except that it's the natural world doing it all on its own, so he called it "natural selection."
Humans do have an effect on the species around us. Frequently a detrimental one. But to the species themselves, it doesn't matter. They don't and can't distinguish between a "natural" change in their environment and a human one.
DNA that is currently the model we are using to trace today's living organisms back to their ancestors is going to be difficult and very confusing and it is not going to make sense since human influence has changed the normal flow of gene mutation and natural selection is now not natural in many species that we share this planet of today.
We haven't. And even if we have it doesn't matter. To DNA there's no difference at all between a change in the environment due to natural causes (say, a forest fire) and a change in the environment due to human causes (say, logging.)
To DNA there is only random mutation and natural selection. The same phenomenon used by the pigeon breeder to alter pigeon populations is at work in nature, altering species by natural, unguided means.
Just this fact alone, we have to consider if humans have the ability to affect and alter nature, then some other mechanism also had the ability to alter global landscaping and all of the organisms that supported it in the past.
That mechanism is natural selection and random mutation.