RICHARD LEAKEY and ROGER LEWIN. The Sixth Extinction: Patterns of Life and the Future of Mankind. New York: Doubleday, 1995. 254 pages. $24.95.
The aftermath of a forest fire is all too well known to us. Every fire season in the forest states, the evening news will show at least one charred scene of smoking hulks of once vigorous old growth. Yet soon thereafter, the first signs of recolonization appear amid the few survivors -- ferns and fast-growing opportunists whose seeds quickly arrive with the wind -- and these new forms and survivors combine to create a new, if often short-lived kingdom: the kingdom of weeds. So too can mass extinctions, short periods of intense species extinctions, be viewed. The few pallid survivors of these great catastrophes of the earth's distant past, such as the great extinction ending the Age of Dinosaurs, are all too often ecological generalists, the evolutionary equivalent of weeds.
The field of paleontology has been consumed for nearly two decades now with ongoing and vigorous research into these greatest of all evolutionary events: mass extinctions. Acting on a planetary scale, the removal of the majority of species opens the way for evolutionary innovation. In this regard, then, perhaps, like the forest-fire analogy, mass extinctions are not such bad things; forest fires, after all, seem to play an important part in maintaining the health of forests on a regional scale. Might not mass extinctions be similarly good for the planet? After all, had a large asteroid not struck the earth 65 million years ago, the Age of Dinosaurs might never have ended, and it would certainly be problematical that a handsome mammal such as I would be writing this book review. But hit it did, and here I sit. I for one am happy that the fifth great mass extinction, which ended the Mesozoic Era, unfolded in its swift and world-consuming ferocity.
If the last one was a good thing, what about the next one? …