This PhD research aims to increase understanding of the causes of global evolution and extinction in the deep sea. This is addressed by focusing on the enigmatic extinction of a distinctive group of cosmopolitan deep-sea benthic foraminifera during the late Pliocene-Middle Pleistocene "Last Global Extinction" (LGE) (3 - 0.12 Ma). This so-called "Extinction Group", comprising nearly 100 species from among others the Pleurostomellidae, Stilostomellidae, Plectofrondiculariidae, Glandulonodosariidae families (c. 25% of deep-sea foraminiferal diversity at that time) all shared a similar morphology of elongate, cylindrical and uniserial tests with small, specialised apertures. To find out what type of change could have been so all-encompassing to decimate and wipe out this major group of foraminifera, we are documenting the history of the "Extinction Group" through the Cenozoic in a number of oceans. In this study, we present the results on the occurrence and abundance of the "Extinction Group" species at ODP Sites 689 (Southern Ocean) and 1211 (North Pacific Ocean). The data indicate good adaptation of the "Extinction Group" to the warm and less oxygenated Greenhouse World oceans (65 - 33.5 Ma), and a gradual decrease in relative abundance and diversity towards Icehouse World conditions (33.5 Ma - present). The LGE itself was coeval with the pulsed expansion of the northern hemisphere ice cap, rendering deep-sea conditions colder and more oxygenated during increasingly severe glacials. The dominant hypothesis therefore, states that the decimation and final extinction of the "Extinction Group" was caused by the inability of the extinct taxa and/or their food supply, to cope with these large and rapid changes in the deep-sea environment. We use proxies to investigate the relative roles of a number of palaeoenvironmental factors in determining the abundance and taxonomic turnovers of our species within the "Extinction Group".