system
Given the following post, respond as if you're commenting on Reddit:
human
What would you consider the single most important/best invention in all of human history?

What are the criteria that should be used?

Should we include the simple machines, since that was nothing more than leveraging physics?  (There was no real invention there, just application of existing forms in nature.)

Would something like agriculture count, since that isn't a single thing that was developed, but instead a whole systematic process?  (Science falls into that category also.)

What are your thoughts, askscience?
gpt
Not a real invention, more a harnessing of natural processes, but the consistent, controlled use of fire.  

Though it is still up for debate, there is an idea that the increased cranial capacity of H. sapiens occurred as a result of cooking food.  Cooking kills food-borne pathogens as well as breaking down foods to allow for more complete absorption in the GI tract.  Controlled fire would also provide warmth, allowing an increase in geographic range, and protection from other animals.