Chapter 4 : The Luck of the Ammonites (Angel Jorge)

In Chapter 4 of Elizabeth Kolbert's The Sixth Extinction,  the reader is introduced to a small town named Gubbio in Italy. In the small town there is a gorge with steep, smooth walls. In the 1970s a geologist named Walter Alvarez discovered the traces of an asteroid, which was later decided was the one that wiped the dinosaurs to go extinct. Alvarez originally went to Italy to study plate tectonics and found layers of marine fossils beneath the surface of the Earth. He also noticed that there were layers of clay, containing no fossils, imbedded in the limestone of Gubbio. His father, Luis Alvarez, suggested that he test the layers of clay for a radioactive element called iridium. Walter found that the clay contained large amounts of iridium suggesting that the clay could have come from an asteroid and that some of the iridium was dating back to the dinosaur period. In 1980, the Alvarez duo wrote a paper explaining that an asteroid struck the Earth killing the dinosaurs. Like many theories that explain the natural history, it was met with many criticisms. However, the asteroid theory proved to be strong because it explained the "fossil gap" that went along with the extinction of the dinosaurs. It explained why certain layers of the Earth were rich with iridium and what happened to the dinosaurs during the Cretaceous period. Kolbert meets with Neil Landman, a paleontologist who specialized in ammonites who was based in Princeton. Kolbert's travels to Princeton are important because she sees the consequences of catastrophes. The ammonites used to be a flourishing species but after the asteroid hit their adaptations proved to be unreliable. For millions of years, ammonites survived but the global event was too rapid for the ammonites to prevail. This chapter shows the vagaries of natural selection. Some people have understood natural selection as a linear process where nature chooses who has the best traits and they survive but the story behind the ammonites and nautiluses shows the randomness of NS. This relates to the theme that science constantly changes the way we understand the world as many people would believe natural selection to be a linear process yet it is actually very random. "Ammonites produced a very tiny egg, only a few hundredths of an inch across. The resulting hatchling or ammonitellae had no means of locomotion; they just floated near the surface of the water, drifting along with the current. Nautiluses, for their part lay very large eggs among the largest of all invertebrates, nearly an inch in diameter," (Page 83). This quote shows he differences between the two species and one of the reasons ammonites' advanced adaptations didn't help them in a catastrophic event.