On the development of maths. It was natural and inevitable. As simple as counting. Counting is the basis of all math. The breakthrough is the symbiology. The alphabets of math, dt4/7-)=+10xyz.
Neither Newton nor Leibniz invented calculus they wrote about it to explain it. The relationship between location, velocity and acceleration were already understood by people working with things that were moving. They understood the difference between a fast horse and a quick horse. Newton's breakthrough was the development of the symbiology that we mostly use today to write differential equations and of course with that symbiology we were able to manipulate those equations to create new understanding.
TEK