The dolphin system is not complex enough. We know this because their brains are not as complex as ours. If we relied on a system comparable to theirs, we'd be failing to communicate a huge amount of what we are capable of thinking.
The question isn't really 'how complex is the dolphin communication system?'; but rather 'how complex is it capable of being, with a different brain in control?' That they haven't produced a system of complex grammar like ours doesn't mean they can't make enough noises to do so.
Perhaps a better example is birds. Some birds can produce a much greater variety of noises than ours, and they do so without the oral apparatus of humans. We could make do with a fairly simple hole - no teeth or tongue necessary. What we'd need is some sort of internal apparatus similar to a bird's syrinx. It wouldn't need to be as complex as the most complex amongst birds, since we don't need to be able to make noises like a lyrebird for human communication. We'd need to make the anatomy somewhere in the trachea a bit more complicated, but in exchange you wouldn't need the complex anatomy that we currently have around the junction of trachea and oesophagus, and choking on food wouldn't be an issue.
If you want to let me find the evidence for your theory, then I will present some.
Just don't expect it to be particular good evidence that I find.
On the other hand, if you can think of something real solid that supports your claims, bring it forward.
Sorry for slow reply, I had overlooked your reply until now.
My sarcastic response with the Google was because I didn't really understand why you were asking me for evidence. You wouldn't ask me for evidence if I claimed that the sky was blue, or that people had heads, so I wasn't sure why I needed to prove that parrots can talk. Here's one, though, if it's really necessary.
Hi Caffeine, some folks say , "Parrots do not really talk, just mimic human speech."
I have as pets, both a African Grey and a Yellow head Amazon . They do talk and know what it is they are saying.
The long term Avian Learning Experiment suggests that some parrots, at least, can ascribe meaning to the sounds they produce, and can understand a simple grammar. Like NoNukes says, though, avian cognition isn't of relevance to the topic. The question is simply whether the trachael anatomy of birds allows them to produce a large enough variety of sounds for human-like communication. This is so obviously and undeniably true that I'm a bit baffled what Jon is being so obtuse about.