evolution is happening even today - observe your next generation - you'll know. So, man's ancestors were surely apes, monkeys and chimpanzees. This does not make RaamaayaNa unreal. On the contrary, it proves that man could live with intelligent animals. There can be many other explanations. It may also be an inspiring piece of writing that makes common men revere other species and not hunt them down for food. Through RaamaayaNa, Waalmeeki might have tried to foster respect for other animals, esp vultures (often seen as evil in folklore), monkeys (seen as a nuisance), bears (seen as vicious). It talks about mutual harmony among species - so the RaamaayaNa is much more important than you think.
The jury is still out on Adam's bridge but it is indeed interesting to note that the bridge exists where the RaamaayaNa describes it and it exists in much the same way. It might have been a natural one that Waalmeeki tried to explain in his book. Or he might have been witness to or heard of its creation by living beings.
The very fact that folklore does not live for a billion years proves that Raama could not have existed so long ago. In your own descriptions, the pointers to the time are all different. Thus, it is very possible that Raama might have existed just 5000 years ago.
