According to some scientific research I've done (and been taught) Apes cannot speak because of a few reasons... However, two being: they do not have the vocal chords like humans and their brain is not as capable as ours to produce, understand, and completely grasp language.
Now, according to evolutionary theories in our society today, we evolved from Apes (Great Apes) and so at one point in history our vocal chords and our brains must have been unable to produce speech as well... (understand we are speaking in millions of years).
If we happen to survive long enough to make it millions of years into evolution humans will be more intelligent than Apes still, but Apes may be as intelligent as humans are now!? They may be able to develop a language and more advanced cognitive behavior like Humans do...
Now, if this were to be true, where would this leave us in relations to interaction with apes? Is knowledge a exponential factor in which we will believe we are so much smarter than these Apes still that we don't want to associate with them (as in let them live in our homes and speak to them like we do other people now). OR will we be able to develop a relationship with them as a co-species?
When you look at this question it raises even more questions into whether we should be using apes and monkeys for lab tests or hunting them for whatever reason?
This can apply to all evolutionary creatures on Earth... according to the science we were all once irrelevant bacteria that could do nothing. So, if these creatures have the opportunity to evolve and become more intelligent will we stop eating them, hunting them, or testing on them? If an ape could converse with you, would you still inject them with the latest vaccine that is still in testing? If the answer were no, then we are testing on these species only because they are not as intelligent (in some sort of sense) as us. This argument in this context makes no sense, because should we be doing it at all then? We would not harm or test on our family that happens to have Downs Syndrome simply because he/she is not "as intelligent as us". So where do we draw reasoning for doing this to animals unless we believe somehow it helps them. If violent acts like this aren't stopped by humans will they be stopped by evolution?