What individuals can you remove from history and actually prevent major discoveries or events?
I heard someone say recently that if Christopher Columbus had never been born, some other European explorer would've landed on the New World more-or-less around the same time. Events would play out differently, but there's not really a circumstance where no one lands in the Americas around 1500.
It made me wonder who could you pluck out from the timeline and actually prevent major events. For example, if Gavrilo Princip had never been born and thus Archduke Franz Ferdinand wasn't assassinated, does World War I still happen, only with a different match lighting the fuse?
Does the Roman Republican turn into an empire without Caesar? Can the US win independence with a different general leading the continental army?
Are there scientists so singular in their genius that, without them, their discoveries could never have been made by someone else?
What about artists? Does film become a popular medium without the Lumière brothers?
I'm sure there are big, obvious ones I'm not thinking of.