The fragmentary nature of the record meant that the semblance of abrupt change was just
that: “With respect to the apparently sudden extermination of whole families or orders,” it
must be remembered, he wrote, that “wide intervals of time” were probably unaccounted for.
Had the evidence of these intervals not been lost, it would have shown “much slow
extermination.” In this way, Darwin continued the Lyellian project of turning the geologic
evidence on its head. “So profound is our ignorance, and so high our presumption, that we
marvel when we hear of the extinction of an organic being; and as we do not see the cause, we
invoke cataclysms to desolate the world!” he declared.