I have a basic question about evolution, for which I never found an answer. I understand how evolution works if we focus on one specific organ or trait. With each generation, some organism is more likely to reproduce, so the trait that leads to success gets more frequent. My problem is understanding how all the traits can evolve simultaneously.
Looking back to our ancestors, we evolved many different kinds of adaptations (in unrelated areas like eyesight, kidney efficiency or a healthy fear of predators, digestion of certain nutrients, balanced walking etc.). Natural selection can only work with what's there, so mutations are important. But if mutations are rare, it seems unlikely that many (thousands of) properties of organisms get improved in a single generation. You'd need to get very lucky to randomly improve all the genes responsible for it.
So, if we look back to our ancestors again, did they just improve on a single or a handful of traits in each generation? In that case we would need hundreds of generations before we have improved somewhat on each "front". By then, the other properties could "drift" back to a not-so-advantageous version. (This was supposing that each generation improves on a random trait, as opposed to long sequences of generations each improving on the same). Or were there always some super lucky organisms that randomly got an improvement on almost all different traits? But just having some of those super lucky ones is not enough. The good traits don't guarantee success, just improve the odds. So we'd need many very lucky ones in each generation.
Has anyone calculated or simulated how the adaptation for many different traits can happen simultaneously?