Haven't chimps already been evolving in tandem with our last common ancestor for millions of years? Why should they suddenly fast forward their evolutionary progress now that we are observing them?
This may be what you are driving at, but in case it isn't: The impression that chimps are suddenly rapidly evolving may simply be a consequence of us watching them closely. We may simply be noticing behaviors that have been present for much longer.
I've heard (think it was from the BBC Life series) that human evolution has sacrificed a lot of jaw muscle and other skull-related ruggedness as compared to monkeys, making room for bigger brains. Since this was obviously not a worthwile tradeoff for chimps etc. in the past, why should it be now?
My understanding is that this is due to heating food after early humans learned to control fire. Cooked food is more nutritious, and easier to eat, and can last longer without spoiling. This leads to the ability to allocate resources in the body more effectively (to the larger brains, versus muscles for hunting) and removes the need for extremely powerful jaws.
Not only. We are generally far weaker than chimps. Their muscle fiber allows for much more strength than us. But strength is useless when you're smart enough to work around it.
They may not be, as others have pointed out, but on the other hand, humans have disrupted their environment and put them under extreme selective pressure of various kinds. We have also reduced their population, creating a greater likelihood of inbreeding, which allows new variations to spread very rapidly throughout the remaining population.
So it isn't our observing them that is relevant. We may be putting pressure on them that is driving their evolution, and evolutionary change can happen very rapidly when the pressure is high.
