This essay explores Earth’s climatory and atmospheric conditions during the late-Cretaceous Period (i.e., when dinosaurs still ruled the Earth), as well as the rapid changes to those conditions thought to have been brought about by the Yucatán bolide (i.e., asteroid) event. Many of the familiar, cosmetic features of Earth’s biosphere that we take for granted today were different 65 million years ago, including: the absence of the polar ice caps; different continental and oceanic layouts; higher concentrations of Greenhouse Gases (GHGs) such as carbon dioxide (CO2) and methane (CH4) in the atmosphere. These prehistoric conditions created an environment that was favorable for reptilian species to thrive in, thereby relegating the various mammalian species to a subordinate role. However, dramatic changes to the planet’s biosphere which contributed to the mass extinctions of over fifty percent of flora and fauna (due to the 9.5 km long bolide that impacted our planet), turned the tables on Earth’s dino-overlords, thus paving the way for the rise of mammals.
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