Being inquired on the three most important inventions, I can't help but refer to my interest in fundamental things. Rather than expected things; the Internet, the automobile or something pertaining to modern medicine, more fundamental items that have allowed these to be invented seem more important to me. For example, the printing press, precursor to the Internet, would be my third on my list of important technology.
Oh! how many papers I've done on the printing press throughout primary school, as I'm sure others have. We take the importance of this gadget for granted and view the research of it as a chore. Well, it may be a chore. However, it has in every way increased the flow of information and allowed an industry of information to develop in a way attainable to the common man. An educated common man is quite important, yes? On to the item that would appear second on my list, though.
Once again, fundamentals! Clothes, am I right? Those are pretty important, keepin' people warm and all. I wear clothes all the time and have acquired an entire wardrobe of them over the years, making them substantially more attainable and, in turn, more common man-friendly than the printing press or its products. I especially like the inventions of the pleated trouser and t-shirt, despite my love of fundamentals suggesting I may enjoy the loin cloth or some even cruder dress. Anyway, on to my choice of the most important invention of man.
The proper treatment and preparation of food, pertaining mostly to meat. Pretty fundamental and important, huh? It's inarguable that this increases the life expectancy of humans exponentially. Honestly, what could be more important than living longer without being poisoned every time you consume a carnivore's feast? True enough, many of our relatively less fundamental inventors were vegetarians and whatnot (I'm talkin' about you, Da Vinci!), but I'd assume most weren't. In short, death prevents progress.
To conclude this, I'd like to offer a glimpse of a world without these inventions/invented processes: we'd be naked, utterly uneducated people and (probably) dead. That doesn't sound like a pleasant world. The modern medicine and health or diet reminders of the day may increase life expectancy by a few years; the Internet may allow information to travel more frequently and efficiently, and clothes... well, clothes are still clothes... Never the less, the point at hand is fundamentals are more important than anything modern man is doing. Rather, modern man's efforts are mere elaboration on his ancestors' original ideas, making original ideas more important, in my opinion.