In this chapter Darwin discussed patterns of appearance and disappearance of species in the geological record.
Of extinction, Darwin wrote,
“The old notion of all the inhabitants of the earth having been swept away at successive periods by catastrophes is very generally given up. On the contrary, we have every reason to believe that species gradually disappear, one after another, first from one spot, then from another, and finally from the world.”
Darwin’s understanding of extinction followed from natural selection as the active agent, and it countered a Victorian-era notion that species had a definite duration fixed by some unknown natural law. Darwin wrote,
“We need not marvel at extinction; if we must marvel, let it be at our presumption in imagining for a moment that we understand the many complex contingencies on which the existence of each species depends.”
Pictured here: the Tasmanian wolf, Thylacinus cynocephalus. The last known wild Thylacine was killed in 1930; the last captive animal died in 1936.
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