Mammals (Late Quaternary), Extinctions of Paul S Martin, University of Arizona, Tucson, AZ, USA r 2001 Elsevier Inc All rights reserved This article is reproduced from the previous edition, volume 3, pp 825–839, r 2001, Elsevier Inc Glossary Extinction spasm or pulse A catastrophic burst of extinctions, peaking in less than a millennium First contact Initial human arrival on a landmass followed by human colonization Late Quaternary extinction event Selective prehistoric extinctions, typically catastrophic, eliminating within the past 40,000 years two-thirds or more of large land mammals of America, Australia, and Madagascar and at least half the species of land birds on remote islands of the Pacific Humans are present or suspected to be present in virtually all cases Megafauna Large terrestrial vertebrates variously defined as 41, 410, and 444 kg adult body weight Equivalent to 100 pounds and similar to the average weight of adult humans, a body size exceeding 44 kg is easily visualized and is adopted here Introduction: Prehistoric Extinctions The late Quaternary extinction event (LQEE) is best known by the loss of large mammals (megafauna) from certain continents Familiar faunal examples of the LQEE include woolly mammoths of the Northern Hemisphere, woolly rhinos in northern Eurasia, ground sloths and glyptodonts in the Americas, and diprotodonts and giant kangaroos in Australia Comparisons between landmasses are revealing The continents differ significantly in both the magnitude and in the timing of their extinctions First Australia, then North and South America, and lastly Madagascar (the Island Continent) rapidly lost two-thirds or more of their large mammals (Figure 1) In contrast, losses were comparatively gradual and much less severe in Eurasia and Africa Although small animals of the continents seldom suffered extinctions, thousands of endemic mammals, birds, and reptiles vanished from oceanic islands At least 85 genera of large (444 kg) mammals, half of the terrestrial megafauna of the planet, disappeared from the continents in the past 100,000 years Now ‘‘out of sight, out of mind,’’ the extinct mammoths and other large animals of the Quaternary coevolved with modern plant species, thereby shaping certain features of vascular plant anatomy and biochemistry Undoubtedly, the extinct species were just as influential as living megaherbivores in determining the structure of natural communities (Owen-Smith, 1988) Before 13,000 years ago the diversity of large mammals in the New World would have resembled that currently found in African or Asian game parks Megafaunal extinctions have made it difficult for ecologists to envision the multiple stable states prevailing in evolutionary time In the absence of their megafauna, the Encyclopedia of Biodiversity, Volume Quaternary The ice age of at least the past 1.81 million years, including the Pleistocene and the Holocene, the latter representing the past 10,000 years Radiocarbon dating An isotopic or nuclear decay method for inferring age of organic materials Carbon 14 is produced in the upper atmosphere by cosmic ray bombardment and oxidized to form C14O2 Distributed through the earth’s atmosphere and oceans, a small percentage is incorporated into a variety of organic materials to decay with a half-life of 5700 years By dating tree rings of known age, and other methods, radiocarbon determinations can be calibrated Although routine application of radiocarbon dating is usually limited to dates of less than 40,000 years, ages up to 75,000 years have been measured savannas, grasslands, riparian habitats, and other biotic communities of the New World, Australia, and Madagascar are not functionally ‘‘natural.’’ Prehistoric settlement on deep-water islands in the remote Pacific began 4000 years ago Extinctions followed, eliminating many endemic birds, reptiles, and land snails along with depletion or size reduction brought by overharvesting of nearshore fish, shellfish, and marine turtles The relatively small number of oceanic islands that escaped prehistoric discovery suffered losses during historic time of such animals as the dodo, Steller’s sea cow, giant rats, and parrots (Figure 2) No late Quaternary extinction pulse is seen in the fossil record of the whales, other marine fauna, or in Antarctica An intense and often controversial search during the past 40 years for an explanation for the cause or causes of the LQEE has failed to yield any widespread consensus among paleontologists, archeologists, paleoecologists, geographers, and other interested parties, many of them convinced of the efficacy of climatic change and of climatic extinction models In recent years, as the global pattern of the LQEE has become better known, much more attention has been focused on anthropogenic models (compare MacPhee (1999) with Martin and Klein (1984)) Always on the scene, humans can no longer be ignored in the search for the cause or causes of ‘‘extinctions in near time.’’ The Comparative Approach In the view of most geologists the Quaternary or Pleistocene ice age of multiple glaciations embraces at least the past 1.81 http://dx.doi.org/10.1016/B978-0-12-384719-5.00090-3 721