^The Kaleidoscope Discovery Engine:
"When we examine discoveries in science and mathematics, in hindsight we often find that if one scientist did not make a particular discovery, some other individual would have done so within a few months or years of the discovery." – Clifford Pickover
This is also true in other advances in human discovery, not just science or mathematics. There's a "the time is right" about new things: Throughout my own life, I've invented things only to either a) find the discovery was done 6 more prior or b) somebody else comes up with a month before or after me.
But I don't fret: a good idea is a good idea no matter where it comes from. And I take pride in knowing that either I was on the right track, or, at the very least, I'm not alone in my ideas.^