Endangered Mammals first major radiation of mammals occurred in the Late Triassic, approximately 200 Ma, and subsequently in the Jurassic Although the diversity of mammals was increasing at this time, with marsupials and placentals in evidence by the Early Cretaceous, these early mammals tended to have small and fairly uniform body sizes A number of hypotheses have been generated to explain both the increase in mammalian diversity and the small body size The breakup and then reattachment of the continents allowed for isolation, speciation, and then faunal exchange, and the development of angiosperm plants also undoubtedly resulted in coevolutionary adaptations and speciation by a wide range of mammals Small body size perhaps was influenced by the dominance of reptiles, which may have forced mammals into a secretive, nocturnal lifestyle where a small body size would be an advantage An explosive mammalian radiation occurred in the Paleocene, again partly from repeated separations, isolation, and reintroductions as continents continued their movements, and perhaps further spurred by the loss of a wide range of large reptilian competitors during the great extinction event 65 Ma for these extinction events The hypothesis that they are climate change-driven is overshadowed by evidence that megafaunal extinctions have coincided, nearly without exception, with human arrival This suggests that the answer lies in the realm of a variety of human-caused situations, possibly exacerbated by climate change They include rapid overharvesting, biological invasions, habitat transformation, and disease Recent Mammalian Extinctions Many island mammal fauna suffered extinction events similar to those that occurred on the continents during the Pleistocene, although most island extinctions occurred in more recent times On islands in the Mediterranean, 13 endemic genera vanished, including small goats and even dwarf elephants; most disappeared approximately 4000 years ago A dwarf form of the mammoth disappeared from Wrangell Island approximately 3700 years ago In Madagascar, eight genera of lemurs, two genera of pygmy hippos, and what is now considered a distinct order, the Bibymalagasia (comprising two species that are variously aligned with the aardvarks and the ungulates), became extinct approximately 1000 years ago In each of these cases human activity, either hunting, habitat alteration, or a combination, is thought to be the main cause Island extinction events have continued into modern times In the Caribbean Islands, five insectivores, 12 rodents, a raccoon, and a seal have all become extinct since 1500 – almost a quarter of all recorded mammal extinctions during that period (Figure 1) Although the total number of mammalian extinctions in recent times does not appear to be large, the current rate of extinction, approximately 0.01% per year, is anywhere from 100 to 1000 times greater than what would be predicted from The Pleistocene Extinctions Between 30,000 and 10,000 years ago, a number of sudden and major die-offs occurred almost entirely among large terrestrial mammals Between 15,000 and 10,000 years ago in North America, a megafaunal extinction event claimed up to 34 genera of large mammals, including mastodons, mammoths, ground sloths, camels, horses, and various large predators such as saber-toothed cats and dire wolves A similar extinction event involving 52 genera of mammals occurred in South America between 12,000 and 8000 years ago In Australia, 14 genera of large mammals disappeared between 50,000 to 32,000 years ago Debate continues on the causes Algeria Cuba Mexico Philippines Guam Cayman Is Palau Thailand Little Swan Is (Honduras) Christmas Is (Australia) Haiti Dominican Rep Martinique 40 St Lucia Barbados Saint Vincent 30 Galapagos Mauritius 20 South Africa Réunion Australia Tasmania (Australia) New Zealand Falkland Is 10 Figure Known mammal extinctions since 1500 Number of species Sardinia (Italy) Bering Straits (USSR) Germany Corsica (France) 189