Technically... probably the wheel.
Without that, pretty much nothing we have would exist.
Sadly. Not impressive. But probably true.
Another vote for the wheel. Everything else hinges on that
Antibiotics? Coffee, possibly. Does that count as an invention?
Electricity. It is used for practically everything around us, short of breathing (But in some cases, also for breathing).
Wheel. The only other one that might come close is writing. Without that we would lose so of who we are.
Man’s best discovery has been learning to make fire
Even writing with a keyboard is still writing.Pretty sure we lost that a long time ago. Lol
Interesting generation. Society has forgotten a lot of roots.
Steam. Yes where would we be without it? Of course we had windmills before that. I guess the agricultural advancements also saw us change from a society barely able to feed ourselves, to one that overeats!I'll go with the ability to harness a reliable source of power; these days, electricity, but steam also revolutionised how we lived in the 18th and 19th centuries.
The development of sanitary systems, such as running water and proper sewerage systems (yes, that includes functioning toilets).
The development of agriculture, cultivating and growing and harvesting crops, rather than foraging for them; this allowed for a growth in population, the development of cities, specialised work forces, and commercial wealth and trade.
Writing; it allowed for the keeping of records, including commercial, and historical records.
Fire: A means of warmth, and cooking food.
More recently: Antibiotics and medical advances.
The wheel is obvious, but advanced societies existed (especially in the Americas) that had never invented the wheel.