Great inventions.

Typically that means big-ticket items. One thinks of dazzling intellectual breakthroughs: the telescope, the steam engine, the airplane, the wheel.... Those were all tremendous, of course.

But often it's some mundane little nothing of a device that changes history. It might be no more than a slight improvement on some earlier invention. If it intersects with a historic moment, it can become a pivot. Then, like the lever that lifts the elephant, it produces consequences far out of proportion to the ingenuity of the thing itself.

I've drawn up a list of nine such items. There might be better examples, but any such list illustrates, I think, the way our lives are interwoven (almost creepily) with the things we make.

1. The chariot. The wheel was great. The cart followed from the wheel and it was great, too. But the chariot? That's just a two-wheeled cart. How hard was it to think of four minus two? And how consequential could that have been? The fact is, the chariot had an immense effect on history. Here's how: In ancient times, the world of farms, towns, cities, workshops, and governments--the "civilized world"--was a belt of territory stretching from the Indus River to Asia Minor. These folks had the cart, which is useful mainly for going straight (it can't turn quickly). North of the civilized belt lived a nomadic people, now remembered as the Indo-Europeans. They invented the chariot, which was really just a basket slung between two big wheels; it was light enough for a horse to pull, and it could pivot as no four-wheeled vehicle could. The horse-drawn chariot gave the Indo-Europeans a crucial military advantage over the sedentary farmers. It spurred their expansion into India, Persia, Mesopotamia, Greece, and Italy, where they overwhelmed and replaced the original inhabitants. That's why English, French, Italian, Greek, Persian, Hindi, and so many other tongues all belong to the same group, the Indo-European family of languages. From America to India, most of us are descended from those nomads.

2. Concrete. Some might say concrete wasn't an invention because it already existed in nature. That's like saying the airplane wasn't an invention because birds could already fly. The Romans figured out how to make artificial concrete by mixing lime, sand, and bits of broken rock with a certain pink volcanic ash. Then they reinforced it with bronze rods. This invention had a precious property: It set and hardened when wet--even underwater. Reinforced concrete could span distances as bricks and stones never could. Using concrete, Romans could build seawalls to protect coastal towns. They could bridge just about any waterway. Rome's conquest of the world and its ability to hold its conquests together rested largely on its ability to build walls, bridges, roads, aqueducts, and monumental buildings. Concrete was the key to all that. The rule of law is often called Rome's greatest contribution to civilization, and maybe so--but concrete has to come in a close second. Check out a historical timeline of concrete and info for kids about concrete.

3. Horse collar. In medieval Europe, the collar that attached an animal to a plow had flat straps that pulled across the animal's chest. Because of the way a horse is built, these straps pressed against the horse's jugular vein and rendered it incapable of pulling a plow. Farmers, therefore, used slow-moving oxen. Then someone invented a collar with softer straps that distributed the weight a bit differently. This tiny innovation allowed the same familiar collar to be used on horses. Horses work roughly 50 percent faster than oxen. Using horses (and a slightly improved plow), peasant farmers could suddenly produce a surplus. A surplus gave them goods to trade at crossroads markets on weekends. Markets soon turned into towns. Towns meant some folks could give up farming and just make goods for sale. A proliferation of such goods meant some people could live purely by buying and selling. You see where this is leading--the horse collar played a pivotal role in ending the feudal system and launching the rise of Europe.

4. Longbow. When people think of major military inventions, they usually think of the gun, which did enable the European conquest and colonization of Africa and the Americas. But if you want to talk about a weapon that triggered the greatest historic change in the least amount of time, the longbow gets my vote. The longbow changed history on three specific days in 1346, 1356, and 1415. On those days, English and French armies clashed at Crécy, Poitiers, and Agincourt. Why was the longbow so important? Because it enabled leather-clad English commoners to defeat ironclad French knights. Throughout medieval times, a European army consisted fundamentally of armored noblemen on armored horses. These living tanks personally won or lost battles, and that's what made nobles noble. At Crécy, Poitiers, and Agincourt, the French army had roughly three times as many knights as the English, but the English army had archers armed with a new kind of bow. It differed from the old kind of bow only in length. But that extra length gave it just enough power to shoot some hundred feet further and pierce armor. Just like that, the armored knight was finished as a significant element in war. From this time forward, power began shifting from the armored class to the moneyed class--which soon came to include merchants, manufacturers, and bankers. Read more about the longbow.