How did the gears start to evolve?
Odds are, they weren't gears in the first place. They were pieces of exoskeleton that came together, allowing a planthopper to jump by moving both of its legs at the same time.
What was the reason that these gears needed to start evolving? Was it an environmental change? Random?
They didn't 'start' evolving. They continued evolving. There wasn't really a starting point (except maybe at the beginning of life itself, and chances are that chemical reactions happened in organic matter before it ever became living). What happened with the planthoppers is that they continued the evolutionary process which was ongoing before they ever emerged as a species, and certain planthoppers started developing exoskeleton leg parts that tended to fit together like gears, giving them a mechanical advantage when they jumped. That gave them an evolutionary advantage which made them more likely to reproduce over other planthoppers. That's what evolutionary adaptation is - an organism within a species is born with something that's different from the rest, and it gives them an advantage and makes it easier for them to reproduce over other organisms that don't have that advantage.. Eventually, that particular change spreads through their species' gene pool. It's a continuous, ongoing process, which is why it's silly to talk about something "starting to evolve".
If it was random, does that mean a human could randomly get a mutation to make him grow wings and fly? if you say humans have no reason to fly, then please explain the reason birds have for evolving flight and why these would not apply to humans.
I suppose it's possible, if marginally, for a human to get a mutation which gives him wings, but mutations simply aren't that energetic. It would be far more probable for it to be a series of mutations that happen over a very, very long period of time.
I for one can think how much wings would help in our survival.
A human with wings would have to be far lighter in order to fly, and they would have to be very large wings. There's a reason birds have such thin, hollow bones, and such a large wingspan for their size. The Andean condor, for example, is one of the largest flighted bird species now living. It's four feet in length from head to tail, weighs between 30 and 40 pounds, and has a wingspan of around ten feet.
Frankly, I'm not sure the trade-off would be worth it.
This is why I found evolution a very hard belief to place your faith into. It sounds much simpler to believe in God. I heard that is called Occam's razor.
That's not what [wiki]Occam's razor[/wiki] is. Occam's razor is that the explanation which makes the fewest assumptions is the most likely to be true. Contrary to popular opinion, it has nothing to do with the simplicity of an explanation. In fact, simpler explanations are more likely to fall afoul of Occam's razor, because their apparent simplicity often masks numerous inherent assumptions. Complicated explanations that don't make assumptions are better than simple ones that do.
That's one of the reasons that religion generally loses ground to science - because science minimizes assumptions when it tries to explain things, and religion generally makes no such effort.