Chapter 4 (Kwasi Obeng-Dankwa)

Chapter 4 begins by talking about a small town a hundred miles north of Rome called Gubbio. This is where Walter Alvarez discovered a few traces of the asteroid that hit the Earth during the Cretaceous period. As he was studying plate tectonics, he realized that the clay within the area had layers of iridium. This led to him, with help from his father, Luis Alvarez, developing the Alvarez theory of mass extinction. This theory stated that man iridium-rich asteroid struck the Earth at the end of the Cretaceous era, killing the dinosaurs. However, it was widely unaccepted by scientists of that time because they believed that extinction occurred gradually and not as suddenly as Alvarez was claiming it did. Scientists of that time also knew about discontinuities in fossil records with a low fossil record for the ending of the Cretaceous Period. While it was explained by stating that more fossils would be found eventually, Alvarez's theory would've made the most sense but very few scientists actually believed in it. Eventually, as more evidence was discovered such as shocked quartz, a layer of sandstone being found, and a crater in Mexico finally made Alvarez's theory widely accepted. We are then introduced to ammonites which are spiral-shaped mollusks. We find out that they went extinct as a result of them producing small infant ammonites while nautiluses which are very similar to them were able to survive as a result of them laying large and stronger eggs capable of surviving changes in temperature.

This chapter connected with the previous chapter, which talked about Darwin's theory and survival of the fittest. This is because of the dying out of the ammonites while nautiluses were able to survive. In the book, it explains that before the extinction of dinosaurs, ammonites were very adept at surviving because of their eggs being small and able to drift through the ocean. However, after the extinction of them, this advantage became a disadvantage and as a result, they were starting to die out and nautiluses were able to thrive. As stated in the book, "Perhaps in the aftermath of the impact, conditions at the ocean surface were so toxic that ammonitellae could not survive, while lower down in the water column the situation was less dire, so juvenile nautiluses managed to endure." This is essentially Darwin's theory, as another organism that was better suited to a new environment was able to thrive while a previous organism found it very challenging to do so. I also found this to connect to the theme: Science is a process. This is because of widely unaccepted Alvarez's theory was until more evidence was found to back it up. Initially, some scientists found it to be nearly impossible as they did not believe such a sudden event could wipe out so many organisms. However, with the discovery of the shock quartz, the crater in Mexico, and the layer of sandstone, it became more accepted. Without this process in science, all theories would be immediately accepted, which would lead to more false information being spread. Yet, with it at first being ridiculed and unaccepted, more evidence can be found in order to better validate it.