This is a meta question. No this isn't a meta question about site, this is a meta question about maths itself.
It has been observed quite a lot of times, that around some point in history,maybe with a gap of five or six years, the same result is independently discovered by two different mathematicians, and a dispute arises as to whom the discovery should be attributed to. It happened with Newton and Leibniz. It happened with Gauss and Bolyai. Why does this happen? Given the large breadth of mathematics(or any science for that matter) what are the odds that two different mathematicians derive the same thing within such short times of each other. Clearly a mathematicians progress and work is heavily influenced by mathematical research going on at that time, but I am not talking about small papers here. Huge, groundbreaking discoveries like calculus and non-euclidean geometry independtly occur to two, sometimes three mathematicians at the same time.
Why? I would assume that there was some other discovery, in maths or otherwise, that promted multiple mathematicians to think in a specific way, and a few of these mathematicians came upon a new result. What were these discoveries in the cases of calculus and non-euclidean geometry then? And as a more general question, this seems to remind one of the truism, "great men think alike", how true is it in this case then? And why?