Do not confuse complexity (e.g. calculus being a harder concept to grasp than evolution) with the necessity of human experience to fuel that "spark" to find new concepts and explore them.

For instance, until maritime travel had reached the point where Darwin was able to go on these multi-year journeys to remote (even by today's standards) islands and see these spectacular creatures, many biologists were limited to their home regions. Not to mention that evolution is on the scale of millennia, something a typical human's lifespan would not be able to easily notice.

One of my favorite examples of this is how I explain the special theory of relativity to people. Einstein published this just a little over a century ago. The story goes that Einstein got his inspiration from this watching a train pass by - he realized that if a light clock (it uses a light photon traveling at the speed of light between two parallel mirrors to calculate time extremely precisely) was on that train, the time on that clock for the person sitting on a bench watching the train go by would be slower than the guy sitting on the train itself. And this difference in time gets faster as that train approaches faster speeds.

It's a mind numbingly simple example. And yet, it wasn't until the early 1900s someone came up with it. Don't discount this human experience (watching a train pass by, which didn't exist in the 1600's) as being a necessary foundation for future scientific inspiration, no matter how simple (or complex) that concept is.

We're in the infancy of space exploration, yet so many concepts about space travel would never have been thought of until the 1950s and 1960s when we actually started sending people and probes into space. One day humans may very well look back and think the same thing "how could they have missed such simple things"

Because Calculus and the mathematics in general don't rely on any empirical based observations. They are entirely created by the generation of, and acceptance of certain axioms. Calculus, ultimately is derived from the same rules that govern 1+1 equalling 2 so it really is only a matter of time when the principles of calculus are 'discovered'(I think verified might be a better word).

As for Evolution, the concept itself is actually pretty darn old, the Hindus and Greeks had a conception of evolution on an abstract level. What I think you are reffering to is Darwinian natural selection which really could only be proposed in an era where the technology to make detailed observations and reproducable experiments exists. That era happened to be around the time of Darwin and, interestingly enough there were various unconnected propositions of theories very similar to Darwins all around the same time.