Terrestrial VS Extraterrestrial
...is Nobel prize-winning father, Luiz Alvarez, analyzed a sample from the town of Gubbio and found a high concentration of iridium in it. To make sure that there was nothing unusual about this sample, they tested other K-T boundary strata from around the world and found extra iridium in these samples as well (np). The abnormal amounts of iridium could come from the earth’s collision with a large asteroid or comet. This puts forth the theory that the iridium was produced not by an asteroid but by an exploding star outside our solar system (Russell, 500). Such an explosion could have blown the iridium off the surface of the moon or directly from the star itself depending on far away it was at the time (500-01). On the contrary, one could reject the exploding star theory, because it does not explain why smaller mammals, crocodiles, and birds, which were also alive during the Cretaceous Period, did not die (Wilford, 220). Another theory is that the dinosaurs were killed off by diseases. This theory rejects the extraterrestrial theories in favor of a terrestrial theory. It is a “solution” to the question of dinosaur extinction that it seems blatantly obvious, according to an eminent paleontologist Robert Bakker (427). This theory gives a biological reason for extinction of the dinosaurs (440-41). Every species of animal carries with it a unique load of disease and parasites (442). These diseases and parasites do not affect the species because its members have developed immunities to them. But because of shifts in the continents during the late Cretaceous Period, shallow seas drained off and land bridges opened up, and thus, species which had never encountered each other before began to meet. As species intermingled, nothing less than biological disaster ensued, as disease and parasites were transferred from one species to another. The new host species of dinosaurs did not have immunities to some of the diseases and parasites, got sick, and died (np). As for the iridium in the soil from the period, it could have been caused by volcanic activity or a collision with a meteor or an asteroid but that such occurrences were simply incidental to dinosaur extinction, not causes of it (np). The problem with this theory is that the extinction during this certain period of time was selective in that only dinosaurs died. What about the birds, smaller mammals, and crocodiles? When the new areas were exposed and easily obtainable to encounter a new species, how come they did not get sick and die off as well? It just does not make sense, because if each species had their own set of disease, they should have followed the rest and become extinct. There would be no life after that period except for plant life. Few paleontologists accept the asteroid theory (Krishtalka, 22). Shifts in the earth’s mantle, where India is now, caused “one of the greatest volcanic events in earth history.” The main eruption occurred sixty-five million years ago. It released vast quantities of the greenhouse gas, carbon dioxide, onto earth’s surface trapping heat from th...