Of course this is just supposition but i would imagine fire was discovered by accident. Perhaps someone was trying to break up a rock to make it smaller for a task by bashing it on another rock. it's possible that sparks flew and ignited some material near by.
Of all the fire by friction methods i would think the plough was the first to be discovered. Not just because Tom hanks used it
. maybe a person was sharpening a stick by using a rock and although the rock was good at cutting it splintered the wood every time. the person then turned to rubbing out a spike on the stick by using a kind of plough method on a log or something.
maybe the plough was a failure for producing fire because of the lack of oxygen to the tinder and indeed any tinder but, it was excellent at rubbing out spikes or spears. the plough method of producing fire kept it's secret and the person not even having an inkling of the secret was non the wiser except for finding a good way of wearing down wood. One day a person wanted a hole in a piece of wood and used his rubbing stick to rub out a hole, the rest being history.
Wouldn't it be wonderfull to be there at that ureka moment that the first flame was produced by man! The beginning of science, the dawn of an age?
being able to see what lay deep in the back of a cave for the first time. To bring light to darkness. Is it any wonder the sun has been worshiped through the ages?
I wonder what the exact date was?, the time and place, was it night or day?, What wood was it that man first burnt?, how long did it take him to realise that meat could be cooked with it?
Was it just fire or was it the great flaming magik on the end of a branch that gave man the spirit and push he needed to evolve above the rest of the animal kingdom? Was it the moment that religion was born, when man realised the sun could be brought from the sky to the earth but he was akin to it, part of it, master of it?
Of course man was always more intelligent than beast but fire gave him the edge. It removed the cold, it made the day longer, it fought the beast or at least kept it at bay.
How long did the secret take to travel across continents and how far had man with fire progressed in learning by the time he reached man without fire? the learning curve of that particular tribe must have been so steep and rapid that, well, i wonder if that was a defining moment between two types of man?