Posted on June 30, 2021 - 8:00am
Why does North America have so many trees and so few elephants?
One of the many mysteries in the fossil record is the late-Quaternary extinction, that wholesale shift of plant and animal life as the Ice Age ended at the close of the Pleistocene and the beginning of the Holocene, a die-off that included about half of the world’s large-bodied animals. Forests grew up, and into the tar pit went the saber-tooth tiger, giant horses, five-ton sloths, and honking big mammoths and mastodons.
Any third grader can tell you what killed the dinosaurs: an asteroid that smashed into Earth 66 million years ago, obliterating T. Rex, Triceratops, and Velociraptor, and paving the way for mammals to thrive.
But that theory was wildly controversial when first introduced in 1980 by Berkeley Nobel laureate Luis Alvarez and his son, Walter, a UC Berkeley paleogeologist. Their idea plunged the paleontology community into decades of acrimonious debate before it became the accepted explanation. Now the theory is being challenged once again.
When we begin to appreciate the idea of rocks as recorders of the truly ancient history of the Earth and start to learn what happened in that history, we experience a dizzying but exhilarating expansion of our appreciation of time. It’s like taking off in an airplane, rapidly climbing to cruising altitude, and suddenly seeing our narrow surroundings unfold into a vast and intricate landscape—in this case the landscape of history.
-Walter Alvarez, The Mountains of Saint Francis