How many generations/years of directed breeding to turn my parrots into Tyrannous Rex (-like creature)? It’s a descendent so it should be easier than for instance Homo Sapiens to dinosaur.
Bonus question: has man made breeding ever resulted in a truly new species (unable to mate with the original population)?
Well the parrots are already dinosaurs, so there’s zero generations for that.
How long it would take to breed a giant carnivore with dagger-like teeth can only be speculative. All that can be said is that transformations of similar magnitude in the past under natural selection have probably taken at least 5 to 10 million years (generations). Under intensive artificial selection it would probably take less time. However, at least some of the changes would require appropriate mutations to take place, and that could take a very long time.
Researchers have already managed to produced teeth in chickens. We might be only a mad scientist, a few decades, and a zoning change away from having our own T-Rex problem!
Oops, forgot the lnk:
Paleontologist Jack Horner has already proposed creating a Dino-chicken. However, this would involve genetic engineering, rather than artificial selection of existing genes (or waiting around for appropriate mutations).
Isaac Asimov wrote a story called “A Statue for Father” in which (IIRC) a guy uses time travel or genetic engineering or something to get small dinosaurs to the present, where it turns out they’re delicious! I think they’re called something like dino-chickens, too.
I don’t know if they are a “species”, but the mule is generally considered infertile and not likely to exist without man-made intervention.
Hybrids like this are not considered a species, and I think the OP was asking if artificial selection had ever altered a population so much that it could no longer reproduce with the parent population. I’m not aware of this happening with any mammals.
Also, not clear that the OP was implying this, but birds are not descended form T-Rex. They share a common ancestor.
Would it not be more sensible to ask a biologist rather than random folk on the interwebs?
That sounds clever at first glance but the two groups aren’t mutually exclusive especially on this board. For example, Colibri, one of the first responders in this thread, is a world renowned ornithologist in case you didn’t know that. We have plenty of other professional biologists and other scientists as frequent contributors as well.
I am not sure why you think that many people that post here don’t have the credentials to back up what they are responding to. This isn’t Yahoo Answers.
Oooooh… that would make a great sig line.
New around here, aren’t you?
The thing is, we’re not “random folk on the internet.” As the tagline says, we represent “thousands of the smartest, hippest people on the planet, plus a few total dipsticks.” (Identifying the latter is left as an exercise for the reader) 
This board attracts a wide range of professionals and other experts, not to mention very well-read amateurs. As Shagnasty mentioned, I am a professional ornithologist with 35 years of experience, with some knowledge of genetics and paleontology as well. We have many other posters with expertise in science, some with advanced degrees. (I believe we have dozens if Ph.D.s posting here at a minimum.) So posting a question like this here is one of the best ways to get it answered.
Hey, I am a random guy on the internet.
Or at least, that’s what I want everyone to think. Actually, I’m a clever dog. Oops, outed myself. Not so clever after all, I guess.
Regarding “birds are already dinosaurs,” that’s true cladistically, but by that definition, we’re all trilobites, aren’t we? (OK, not quite the correct example, but you get my point.)
In any case, we’d also have to create an artificial environment for them to live in. I doubt many dinosaurs would be viable today.
Another issue is how many retro-birds are we allowed to (or can we afford to) keep alive at any given time? If it’s just a breeding program, the limit is vanishingly small (which is one of the problems with breeding programs). Evolution takes not only a lot of time, but it also takes a lot of individuals. Oddly, though, it’s not a “the more the merrier” thing. The bigger the population, the more stable it tends to be, if I understand it correctly. To get dramatic morphological changes, you need a long series of events where populations get put under the pressure of dramatic changes in environment, and to get speciation, you need to separate populations – divide them.
In any case, it’s a long friggin time, and you won’t get back to what dinos were like, you’ll only get to something that resembles them. Chance is a slippery slope that is not easy to climb back up.
Just one, but you’ve got to be really lucky on the mutations.
Since one of the repeated (false) memes of creationists is that “speciation has never been observed,” you can find various lists of these on the internet. Here’s one: Observed Instances of Speciation. Some of these are speciation events in the wild, but a lot of them are lab-created. Note that to observe these in human lifetimes you need something with a fast generation time: fruit flies, bacteria, that sort of thing.
Polyploid plants are sometimes considered different species, and they’re really easy to produce.
Well, no. Trilobites are on quite different branch of multicellular animals than we are; we are not part of the same group. A better analogy would be saying that we are apes, or monkeys, since we are nested within that group. Birds are dinosaurs in the same sense.
I know the molecular scale evolution changes better, but the simple answer is going to be somewhere between more than you’d expect and impossible. Parrots are already too specialized in too many ways to be able to undiscover their traits and go back to the “parental” traits.
The simplest place to look for the new species question is the farmyard- I think that humans haven’t so much made a new species as destroyed the parental one. I’m thinking of cattle’s ancestor the auroch. Chickens and pigs and certainly dogs and cats, I believe, would be able to find a wild relative with which to still mate and those are all in the many thousands of years. Now plants are another story and domestication of those has certainly led to new species but most of these are annual reproduction which means 1000s of generations could have been used to create the speciation event.
Funny.
Not tyrannosaurs, but apparently maniraptoran dinosaurs in their own right. New research suggests that a change in the rate of fetal development may be the main/only thing separating birds from dinos:
http://news.discovery.com/animals/dinosaurs/birds-dinosaurs-120530.htm
There’s this belief going around in some circles that, for instance, birds have all of the DNA needed to revert back to a T-rex just hiding in their genome, and if we could just reactivate it, we could make dinosaurs. Part of this was fueled by the discovery that there are indeed inactivated genes hiding that can make teeth (or at least tooth buds) in chickens.
But a whole dinosaur? No way. It’s just not true. Genetic information gets lost over evolutionary time if it’s not being used. The tooth genes have stuck around, but they’ll end up degenerating sooner or later, and the vast majority of the sequences you need to make a dinosaur are long gone.
I’ve been learning a lot more about dinosaurs now that I have a three-year old boy and I wasn’t previously aware of the large size of some of the presumably feathered dinosaurs.
If you want to take a modern bird and breed it into a dinosaur, I suggest starting with the cassowary. To my untrained eye, it’s nearly indistinguishable from images of feathered dinosaurs.