Biological Extinction | Paul R. Ehrlich
Casina Pio IV
How to Save the Natural World on Which We Depend
Casina Pio IV, 27 February-1 March 2017
On our 4.54 billion year old planet, life is perhaps as much as 3.7 billion years old, photosynthesis and multi-cellularity dozens of times independently around 3.0 billion years old, and the emergence of plants, animals, and fungi onto land, by at least the Ordovician period, perhaps 480 million years ago, forests appearing around 370 million years ago, and the origin of modern groups such as mammals, birds, reptiles, and land plants subsequently. The geological record shows that there have been five major extinction-events in the past, the first of them about 542 million years ago, and suggests that 99% of the species that ever lived (5 billion of them?) have become extinct. The last major extinction event occurred about 66 million years ago, at the end of the Cretaceous Period, and, in general, the number of species on earth and the complexity of their communities has increased steadily until near the present.
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