I've thought about this as well and besides from pseudo-scientific bullshit that we are somehow telepathically connected, my conclusion is this:
Similar cultures. Take for instance the event of the light-bulb. Without electricity, there could be no study on the field of electronics. With the event of electricity however, people could develop that field of science. Some tried to find means of transportation through electricity, and some tried using communication, i.e. the telephone, which was also simultaniously discovered. Some tried to invent a source of light with this new knowledge of electricity, and one succeeded.
Discoveries are tools in the development of technology. When new discoveries hit the ether it sometimes creates a new field of science, and that makes different scientists race to exhaust that field. Development of technology, like the development of society, is not in any way bound to an initiating individual. Instead, we have a culture in common, with it's ups and downs and its own way of progressing. Without Newton, we would have the theory of gravity explained by someone else. With no Hitler (not a big fan of Hitler) we would have another leader for the Nazi-party instead.
Highly philosophical though.