A Short History of Nearly Everything (2003)

Descended from the apes! My dear, let us hope that it is not true, but if it is, let us pray that it will not become generally known. - Remark attributed to the wife of the Bishop of Worcester after Darwin's theory of evolution was explained to her

I had a dream, which was not all / a dream. / The bright sun was extinguish'd, / and the stars / Did wander . . . - Byron, "Darkness"

Because we can't see into the Earth, we have to use other interesting techniques, which mostly involve reading waves as they travel through the interior, to find out what is there. We know a little bit about the mantle from what are known as kimberlite pipes, where diamonds are formed. What happens is that deep in the Earth there is an explosion that fires, in effect, a cannonball of magma to the surface at supersonic speeds. It is a totally random event. A kimberlite pipe could explode in your back garden as you read this. Because they come up from such depths - up to 200 kilometres down - kimberlite pipes bring up all kinds of things not normally found on or near the surface: a rock called Peridotite, crystals of olivine and - just occasionally, in about one pipe in a hundred - diamonds. Lots of carbon comes up with kimberlite ejecta, but most is vaporized or turns to graphite. Only occasionally does a hunk of it shoot up at just the right speed and cool down with the necessary swiftness to become a diamond. It was such a pipe that made South Africa the most productive diamond-mining country in the world, but there may be others even bigger that we don't know about. Geologists know that somewhere in the vicinity of northeastern Indiana there is evidence of a pipe or group of pipes that may be truly colossal. Diamonds up to 20 carats or more have been found at scattered sites throughout the region. But no-one has ever found the source. As John McPhee notes, it may be buried under glacially deposited soil, like the Manson crater in Iowa, or under the Great Lakes.
(page 271)

As James Surowiecki noted in a New Yorker article, given a choice between developing antibiotics that people will take every day for two weeks and antidepressants that people will take every day for ever, drug companies not suprisingly opt for the latter. Although a few antibiotics have been toughened up a bit, the pharmaceutical industry hasn't given us an entirely new antibiotic since the 1970s. (page 396)