There have been three great mass extinctions. The first was about 250 million years ago, when almost all the animals that had emerged onto dry land were destroyed. The second, more famous but arguably less catastrophic, was the demise of the dinosaurs about 65 million years ago. The third began at the end of the last Ice Age. Professor Ward, a palaeontologist, describes all three events, giving his view that the first two had complex causes (it wasn't just the asteroid impact that killed the dinosaurs, he believes). This third event is different - there is only one cause, and it is humans. A fair amount of damage is now being caused by well-intentioned scientific invention. Ward is pessimistic, but offers some suggestions that could make the outcome slightly better than it might otherwise be. Ward describes his fieldwork, including underwater episodes with sharks for company, and cites facts and figures, many of which have not been published outside scientific journals.