Simultaneous Inspiration?

I notice, sometimes, before things become trends, that a few people will become inspired around the same time to do similar things. For instance, I've been infatuated with gears for a very long time and have been designing some riveted gear jewelry over the past year or two but I just haven't had time to put the designs into production. Sometime earlier this year I stumbled across Katrinabird's shop where she is sells her gear inspired jewelry. My designs are a bit different than hers but one fact remains clear: it's basically the same idea. I also have designs drawn up for gear screen prints; weeks later I stumble across Moxiemadness' shop where she sells a neon pink gear shirt. Weird; she's doing it, too. Prior to seeing gear stuff being produced I truely don't recall seeing it done elsewhere. Granted, I'm probably wrong. Gears certainly aren't new and I'm sure they've been repurposed a hundred times. Maybe I never noticed those designs before since I wasn't looking out for them. Maybe they weren't there after all. I can't help but feel it's a case of simultaneous inspiration. Another example: a clothing designer friend of mine once saw a design in a fashion show nearly identical to something she had recently made. Neither of those designs had seen the light of day prior to the Fashion show. Neither of them ever accused the other of thieving the idea; they were simply in awe over the fact that they both were feeling the same stuff at the same time.