Question on Manu and Yugas

1. So I think we know that the idea that man and chimps have a common ancestor is a well established **fact**, there's no questioning that, but then what about Manu(Svayambhuva)? If he's a mind-born son of Brahma and gave rise to the whole of humanity, then isn't that just the same concept as adam-eve? Could he be a progenitor in the sense of carrying the ability of jivas to evolve into humans as a species? 2. We know that Ramayan happened about 18 million years ago (24th Mahayug, we are in 28th i believe), but what happens when we take these yuga cycles further back in time, say 200 million years ago? How can yuga cycles exist without humans? Is it necessary that humans be there? Can a yuga be applicable for other species? I know its a lot of questions, but these have been troubling me for a while now, and I will gladly accept any answer.