It is estimated that the global average of Earth’s surface temperature was about 8°C higher than today when the Cenozoic Era started about 66 Ma ago (1 Ma = 1 million years) (Zachos et al. 2001; Zachos et al. 2008). As shown in Chapter 1 (Figure 1.1), the history of the Cenozoic is rather shaky. Temperatures were maintained during the Paleocene epoch, and even increased towards the Eocene optimum (–52 Ma). The entry into the Oligocene epoch was marked by a cooling associated with the first important glaciation of Antarctica. Temperatures were more stable over the next 10 Ma and reached an optimum around the Middle Miocene (–14 to –16 Ma). This optimum was followed by another cooling trend, preparing the ground for the dive into the Pliocene, and then the gradual onset of the glacial–interglacial cycles of the Pleistocene.