He says that we cannot prove what they ate and how their livers worked. The evidence that Gould took supported his theory. The fossils showed a perfectly natural occurrence. Physicist Luis Alvarez came up with the idea of a comet hitting the earth. He discovered that the clay had three times the amount of iridium.
Iridium is very rare in earth, but in comets, asteroids, and meteors, it is very common.
He concluded that the extinction of the dinosaurs may have been because of the collision. He said that the comet might have been some six miles across that may have traveled 40,000 miles per hour. It smashed into the earth creating a crater that was 100 miles in diameter. Temperatures dropped dramatically, and plants would have begun to die. The cloud would have covered the earth in a few weeks.