Metallurgy. Without it, no tools, and without that, no advanced civilization. Though equally important especially from the Greeks onward was math, science, and their application (engineering).
Language, there's no doubt about it. It's more than a tool to help us communicate with one another, its invention (or discovery) enabled the notion of "the self" to become far more apparent than it ever had been before.
Metallurgy. Without it, no tools, and without that, no advanced civilization. Though equally important especially from the Greeks onward was math, science, and their application (engineering).
Difficult choice.
Without mastering fire we would be nowhere.
Without writing we would be nowhere.
Without the wheel we would be going nowhere.
In the end I plumped for writing as it allows us to pass on ideas to many people without it changing.
(Yes, I know that re-writing can change it, but at least this will be slower than the corruption that takes place when word of mouth is used).
Writing
It's how we have been able to go back and truly have accounts of the times before us. Though it obviously hasn't helped us as we seem to keep repeating old mistakes.
Along with many others on here I have to say that fire was not an invention, so that's out.
And while I really wanted to go with music and art, as they're two of my most favorite things on the planet, I think I have to agree with this...
Without writing where would art and music be as we wouldn't have access to some of the greatest masterpieces in history. I don't want to imagine a world without the works of Bach, Beethoven, Mozart, Shakespeare, Van Gogh, Bizet, etc.
ok let me say again .
its metal damn it!
every area in the world had fire, language, wheels, some sort of written language, agriculture, some kind of religion, some kind of currency, ect ect.
and those areas stayed the same for thousands of years with no change, no advancement.
basically primitive man, and in some places these people still exist.
it was the people and the areas who learned to use metal that began the advancement of the human race.
egyptians, greeks, romans, vikings, spanish, ect ect all advanced , conquered and prospered due to their uses of metal...........