I'm into the last three-quarters of it – Bill Bryson’s A Short History of Nearly Everything.
GO OUT AND GET THIS BOOK!
It’s about…. nearly everything!
So I am at this section for a while now, [I’m a fastidiously slow reader…] about pre-history, it’s all about trilobites and whatchamacallits and Cambrian this-and-that-creepy-crawlies -- fossils, basically!
I felt that this one slab of text from chapter 22 was worthy of regurgitation –
If you imagine the 4.5 billion odd years of Earth’s history compressed into a normal earthly day, then life begins very early, about 4 A.M., with the rise of the first simple, single-celled organisms, but then advances no further for the next sixteen hours. Not until almost 8:30 in the evening, with the day five-sixths over, has Earth anything to show the universe but a restless skin of microbes. Then, finally, the first sea plants appear, followed twenty minutes later by the first jellyfish and the enigmatic fauna… At 9:04 P.M. trilobites swim onto the scene, followed more or less immediately by the shapely creatures of the Burgess Shale. [← Unless you are real smart, you must read the preceding chapter to know what this is]. Just before 10 P.M. plants begin to pop up on the land. Soon after, with less than two hours left in the day, the first land creatures follow.
Thanks to ten minutes or so of balmy weather, by 10:24 the Earth is covered in the great carboniferous forests whose residues give us all our coal, and the first winged insects are evident. Dinosaurs plod onto the scene just before 11 P.M. and hold sway for about three-quarters of an hour. At twenty-one minutes to midnight they vanish and the age of mammals begins. Humans emerge one minute and seventeen seconds before midnight. The whole of our recorded history, on this scale, would be no more than a few seconds, a single lifetime barely an instant.
In the next paragraph he goes on to restate it thus:
Perhaps an even more effective way of grasping our extreme recentness as a part of this 4.5-billion-year-old picture is to stretch out your arms to their fullest extent and imagine that width as the entire history of the Earth. On this scale, according to John McPhee in Basin and Range, the distance from the fingertips of one hand to the wrist of the other is Precambrian.
All of complex life is in one hand, “and in a single stroke with a medium-grained nail file you could eradicate human history.”