If we're talking about big science&technology categories, I'd say: Controlled fire (if you can consider it a "man-made creation") -> essential for food and a l

If we're talking about big science&technology categories, I'd say: Controlled fire (if you can consider it a "man-made creation") -> essential for food and a lot of manufacturing Wheel -> essential for transportation, but also to make flour (millstones), and a lot of other stuff (e.g. turbines are, basically, specialized wheels) Controlled electricity and electromagnetism -> artificial light, modern communications, not to mention medical advancements like X-rays Insulin and pecillin -> millions of lives saved the printing press -> knowledge becomes easier to spread If we extend this to all kinds of human "inventions", including law, philosophy, religion, and so on, the list is even longer.