Though we became experimental creatures of our own devising, it’s important to bear in mind that we had no inkling of this process, let alone its consequences, until only the last six or seven of our 100,000 generations. We have done it all sleepwalking. Nature let a few apes into the lab of evolution, switched on the lights, and left us there to mess about with an ever-growing supply of ingredients and processes. The effect on us and the world has accumulated ever since. Let’s list a few steps between the earliest times and this: sharp stones, animal skins, useful bits of bone and wood, wild fire, tame fire, seeds for eating, seeds for planting, houses, villages, pottery, cities, metals, wheels, explosives. What strikes one most forcefully is the acceleration, the runaway progression of change - or to put it another way, the collapsing of time. From the first chipped stone to the first smelted iron took nearly 3 million years; from the first iron to the hydrogen bomb took only 3,000.