The offsprings of interbreeding survive to maturity and are themselves capable to breed under the same conditions, i.e. at least in the lab, and form a colony that does not dwindle for many generations under controlled climate conditions.
Viable-in-the-lab is not the same as viable-in-nature.
Indeed, this is why it is an experiment that allows for compressed timescale. For example, if evolution from species proper to another species proper occurs in specially chosen climate and with artificial insemination, most people would agree that it would be a proof that real-time evolution is also possible, even though in real time it would be much slower.
Simulating such a descent with modifications in a laboratory would be as simple as changing some critical DNA to prevent interbreeding of sub-species
Well, it would depend of what kind of evolution you set out to prove. If you are proving the evolution with random mutations, then you would have to make your mutations perhaps accelerated, but they should also remain random: the intervention directed at getting a particular feature turned off or on would not be a valid experiment.
If, however, you want to prove a weaker hypothesis: that evolution is possible if someone directs it, then of course you can direct your mutations in the way that suits your goals. You still have to show that the descendant species, while not interbreeding, are themselves each viable: produce offspring and form a viable colony. You also have to somehow explain what had directed the mutations in real life.
And why do you even posit it?
Why, because setting aside some speculation how zebra 1 and zebra 2 are somehow "evolution in motion", the direct observation of mammals and birds is that their species are stable: you can only produce examples of speciation by fudging the definition of species, and at any rate you can only point to very similar animals. It ix natural to conjecture, as I do, that species proper do not evolve one to another at all: there is a boundary that does not get crossed.
Theologically it makes perfect sense [...] cry of angst
If evolution were real science you would not need to psychoanalyze your opponents. You would simply use facts and logic.
I have cited before examples of evolution "caught in the act" of speciation -- half way in the middle of forming a new "species boundary" (your term) which prevents them from producing viable offspring.
Of the three species of Zebras, to repeat, two can produce viable hybrids, but the third cannot -- at least not consistently.
Attempts to interbreed produce unusually high levels of miscarriage and still births.
Might some of those Zebra hybrid offspring be viable?
I don't know, but this example clearly illustrates the point that speciation in nature is not a simple matter of one mutation crossing a "species boundary".
Rather, it's the accumulation of many mutations, generation after generation, which leads to a long process among separated sub-groups of increasing difficulty in interbreeding.
So, using your term, a "species boundary" is what forms whenever sub-groups accumulate so many different mutations they cannot produce viable offspring.
By scientific definition then, where there was one species, now there are two, and this is illustrated in countless natural examples.
annalex: "For example, if evolution from species proper to another species proper occurs in specially chosen climate and with artificial insemination... "
Your term "species proper" is meaningless.
The scientific definition of "species" includes the ability to interbreed in nature.
When two different sub-species no longer interbreed, then they are classified by science as two separate species.
So that is your "species boundary."
And the ability of sub-species to interbreed is largely a function of the number and type of DNA mutations which accumulate generation by generation, typically over thousands or millions of generations.
Of course, simulating thousands or millions of generations in large creatures in a lab is impossible in real time.
And not necessary to confirm Evolution Theory, since we can see, through DNA analysis, exactly which mutations separate one group from another.
annalex: "Well, it would depend of what kind of evolution you set out to prove.
If you are proving the evolution with random mutations..."
I don't personally believe that anything is ever truly random, but rather God at some level directs everything.
Exactly where, how and why we will never really know, but the appearance of randomness in nature is one just tool God uses to enact His will, in my humble opinion.
So it's ultimately irrelevant to me exactly how "random" various mutations may or may not have been.
However, you have to ask this question: if God wishes for things to appear "random", would He not in His infinite wisdom have created them to actually be random?
In reference to alleged "randomness", I would invite you to look up the mathematical ideas in chaos theory, and particularly the notion of a "strange attractor".
In that language of directed randomness, God is the Great Attractor, who makes what appears random conform to His plans for the Universe.
That is my theological belief, and it leads me to suspect that we will never find scientifically the "Hidden Hand of God" within the "random" mutations that created all life on Earth, and eventually, us.
That's why as far as science is concerned, by definition of the word "science" these DNA changes were all just "random".
And I have no problem with that -- let scientists do their scientific "thing", as long as it's honest work, it's all good stuff as far as I'm concerned.
annalex: "If, however, you want to prove a weaker hypothesis: that evolution is possible if someone directs it..."
That is hardly a "weaker hypothesis", it's a confirmed fact as demonstrated by innumerable examples of humans working to develop new breeds for agricultural and other purposes.
Selective breeding and careful hybridization alone produce astonishing new varieties, and there is no imagining what might eventually result from DNA engineering.
So "directed evolution" is not a "hypothesis", its a fact.
annalex: "direct observation of mammals and birds is that their species are stable: you can only produce examples of speciation by fudging the definition of species, and at any rate you can only point to very similar animals.
It ix natural to conjecture, as I do, that species proper do not evolve one to another at all: there is a boundary that does not get crossed. "
As now demonstrated many times, all of that simply is not true:
annalex: "If evolution were real science you would not need to psychoanalyze your opponents.
You would simply use facts and logic."
When you claim science is a "cult" and working scientists are "cult authorities" then you have left the reservation of sanity, and entered the realm of psychoanalysis -- tell us poor dear, what is your problem, did some scientist drop you on your little head as a child, and that's why you can't think logically any more?
That is all language of disrespect, regarding which a certain wise Individual once directed we should "do unto others...", FRiend. ;-)