The evidence is absent that any known Species Proper evolve into another Species Proper. It is then is a boundary by laws of nature.
The experiment to falsify this is easy to define: pick the original population, inseminate and manipulate the embryos randomly, emulating a random mutation. Adjust the climate to favor a certain developing feature. Let the sick die and repeat insemination and gene alteration with the healthy adult specimens. Make control inseminations of healthy specimen with the original species. Observe the core population stable, and control inseminations progressively less successful, to the point of becoming impossible.
If this experiment is successful, it will prove the foundation of the evolutionary hypothesis: that given time and changing environment, random mutations will produce a new Species Proper better suited for the changed environment.
Prove me wrong by experiment; not by calling in cult authorities.
Well, first of all, you've "called in" no "authorities" at all, "cult" or otherwise.
So what you express is simply your opinion, and no doubt your religious belief, though for some reason you wish not to admit that.
Remember, the US Constitution's First Amendment guarantees your right to believe whatever you wish regarding religious subjects, and so there is no legal requirement -- zero, zip, nada -- for you to accept as true whatever scientist might say on evolution, or on anything else.
In this regard at least, it's still a free country.
But that's not quite the end of the story, especially for those whose rejection of Evolution Theory supports their religious beliefs.
Because, in case you forgot, while the First Amendment allows you to believe whatsoever you might wish, the Ninth Commandment requires you to tell the truth about it.
And your labeling of normal, ordinary working scientists as "cult authorities" is simply not truthful, and no matter how misguided you've been in life, you can't fail to know that, can you?
OK, now let's look at the merits of your claims...
annalex: "The boundary is a population, let's call it Species Proper, that can interbreed."
There are no "boundaries" on a species, it is simply a population which can interbreed.
When sub-populations (i.e., sub-species) get separated and evolve over time to the point where they can no longer interbreed, then we call such population a separate species.
Among examples mentioned here, Zebras and Elephants consist of populations science classifies as "sub-species", other groups considered "species" and still others in separate "genera."
And when you analyze the DNA of these various categories, what you find is that those sub-species which can interbreed have much more similar DNA than those which cannot.
So the obvious scientific conclusion is that sub-species with more similar DNAs share more recent common ancestors than those species and genera with less identical DNAs.
In short, a simple rule can be observed: the more similar the DNAs, the more recent was the common ancestor, and the more likely is successful interbreeding.
As DNAs become more and more dissimilar, then interbreeding becomes more and more difficult, until at some point -- i.e., African and Asian Elephant genera -- interbreeding is impossible.
Interbreeding experiments to test this rule have been done innumerable times, and always hold true.
Indeed, scientists use such data to help determine whether different populations are just breeds & sub-species, or actually different species & genera, etc.
annalex: "The evidence is absent that any known Species Proper evolve into another Species Proper.
It is then is a boundary by laws of nature."
In fact, evidence is everywhere in nature -- of different similar animals (i.e., Elephants, Zebras) in various breeds, sub-species, species, genera, etc.
I think it takes a willful act of blindness not to see it.
annalex: "The experiment to falsify this is easy to define:"
The "experiment" you define is conducted in nature, by God, every day, every generation and over many millions of years.
Yes, there's no physical evidence suggesting that natural evolution in large creatures happens on time scales of less than many thousands of generations.
But abundant evidence suggests separated populations (breeds, sub-species) continue to evolve until interbreeding becomes difficult and finally impossible.
annalex: "If this experiment is successful, it will prove the foundation of the evolutionary hypothesis: that given time and changing environment, random mutations will produce a new Species Proper better suited for the changed environment."
God has been running that experiment for untold millions of years, and the results we can see: before any two populations evolve into separate species which can no longer interbreed, they first change to become separate breeds (i.e., dogs) which look different but do eagerly interbreed.
Then over time, breeds change into different sub-species which grow more reluctant to interbreed, before they finally evolve to separate species which can physically no longer interbreed.
That's what physical evidence shows us, and it's what Evolution Theory explains.
So what exactly is your problem with it?