Pleistocene Mammal Extinctions

Transcription

1 Pleistocene Mammal Extinctions The late Pleistocene witnessed the extinction of 35 genera of large North American mammals. The last appearance dates of 16 of these genera securely fall between 12,000 and 10,000 radiocarbon years ago ( 13,800 11,400 calendar years B.P.). Whether the absence of fossil occurrences for the remaining 19 genera from this time interval is the result of sampling error or temporally staggered extinctions is unclear. The cause of the extinctions has been exceptionally tricky to resolve in NA because the time of extinction overlaps both a critical one for climate change and the time that the Clovis people flourished, although it is hard to see why a more livable climate would lead to a mass extinction. A short-faced bear Arctodus simus, showing size relative to an adult human. Some weighedover a ton, twice the size of a grizzly bear. There is no question that humans played a role in this mass extinction in a geological instant in North America. Archeological sites that illustrate heavy human predation on large mammals in that time period include the 15,000 year old Mezhirich site 90 miles south of Kiev in the Ukraine there are 4 oval shaped dwelling built of 70 tons of mammoth bones from at least 200 kills (mammoths went extinct in Eurasia in the same period). One dwelling has an outer wall composed of 95 mammoth mandibles stacked on top of one another in a herringbone pattern. A site in Czechoslovakia has over 1000 mammoths.. The most spectacular accumulation of all exists at Solutre in France, where at the foot of a steep cliff extensive deposits more than 3 feet thick contain the bones of 10,000 to 100,000 horses, either driven to their deaths off the top of the cliff or ambushed in a narrow pass down below. (fm The Creative Explosion pg 60). In North America there is ample evidence of the heavy toll that Native Americans could take on the large mammals present in more recent times. A stampede of bison 150 miles southeast of Denver drove 190 of the animals over a cliff A wikipedia page titled Buffalo Jumps notes that Native Americans herded the bison and drove them over the cliff, breaking their legs and rendering them immobile. Tribe members waiting below closed in with spears and bows to finish the kills. The Blackfoot Indians called the buffalo jumps "pishkun", which loosely translates as "deep blood kettle". This type of hunting was a communal event which occurred as early as 12,000 years ago and lasted until at least 1500 CE, around the time of the introduction of horses. On all of the continents and islands where Homo sapiens was a recent arrival during the late Pleistocene and Recent Eras, there were die-offs of large animals. A recent dating of the extinction of a large flightless bird in Australia using an amino acid technique on eggshells indicates 50,000 years ago--just when Aborigines arrived. Moas in Tasmania survived until humans arrived 800 years ago. In 1999 a rigorously tested radiocarbon dating showed that the last occurrence of ground sloths in Cuba was 6250 years ago, around the time that people first arrived there. Ground sloths went extinct on the continent 13,000 years ago. Of course, there was no large extinction event in Africa, where the megafauna and humans had coevolved. In 1839 Charles Darwin wrote It is impossible to reflect on the state of the American continent without astonishment. Formerly it must have swarmed with great monsters; now we find mere pygmies compared with the antecedent races. On pages 3 & 4 are images of 28 species of large mammals that went extinct at the end of the last glacial advance; 64 such species are listed below. Alfred Russel Wallace observed that on a global scale, We live in a zoologically impoverished world, from which all the hugest and fiercest and strangest forms have recently disappeared." compiled by Dana Visalli/dana@methownet.com/

2 Pleistocene Mammal Extinctions in North America Common Name Scientific Name Family Last Appearance (years ago) Xenarthra (anteaters, sloths and armadillos) Beautiful armadillo Dasypus bellus Dasypodidae 11,000 Panamerican ground sloth Eremotherium laurillardi Megatheriidae 11,000 Rusconi's ground sloth Eremotherium rusconi Megatheriidae 39,000 Ground sloth Glossotherium robustum Mylodontidae 9000 Simpson's glyptodont Glyptotherium floridanum Glyptodontidae 23,000 Northern pampathere Holmesina major (3+ species) Pampatheriidae 11,000 Jefferson's ground sloth Megalonyx jeffersonii Megalonychidae 11,500 Florida ground sloth Megalonyx leptostomus Megalonychidae 11,000 Shasta ground sloth Nothrotheriops shastensis Megatheriidae 11,500 Harlan s Ground sloth Paramylodon harlani Mylodontidae 11,000 Carnivora Giant short-faced bear Arctodus simus Ursidae 11,000 Short-faced skunk Brachyprotoma obtusata Mustelidae Dire wolf Canis dirus Canidae 9000 Dhole Cuon alpinus* Canidae 12,000 Scimitar cat Homotherium serum Felidae 10,000 American cheetah1 Miracinonyx inexpectatus Felidae 11,000 American cheetah2 Miracinonyx trumani Felidae 15,000 American lion Panthera (leo) atrox Felidae 11,000 Sabertooth Cat Smilodon fatalis Felidae 11,000 Florida cave bear Tremarctos floridanus Ursidae 23,000 Rodentia Giant beaver Castoroides leiseyorum Castoridae 11,000 Giant beaver Castoroides ohioensis Castoridae 11,000 Holmes's capybara Hydrochoeris holmesi Hydrochoeridae 12,000 Pinckney's capybara Neochoerus pinckneyi Hydrochoeridae ~13,000 Lagomorpha Aztlan rabbit Aztlanolagus agilis Leporidae >31,000 Perissodactyla Mexican horse Equus conversidens Equidae 11,000 Yukon horse Equus lambei Equidae 11,000 Scott s horse Equus scotti Equidae` 11,000 Hagerman horse Equus simplicidens Equidae 10,000 California tapir Tapirus californicus Tapiridae 11,000 Cope s tapir Tapirus copei Tapiridae 11,000 California tapir Tapirus merriami Tapiridae 11,000 Vero tapir Tapirus veroensis Tapiridae 12,000 Artiodactyla Long-horned bison Bison latifrons Bovidae 20,000 Steppe bison Bison priscus (antiquus) Bovidae 8000 Harlan s musk-ox Bootherium bombifrons Bovidae 11,000 Yesterday s (Western) camel Camelops hesternus Camelidae 10,500

3 Diminutive pronghorn Capromeryx minor (3 species) Antilocapridae 12,000 Stag moose Cervalces scotti Cervidae 11,500 Shrub ox Euceratherium collinum Bovidae 11,500 Large-headed llama Hemiauchenia macrocephala Camelidae 12,000 Long-nosed peccary Mylohyus (5 species) Tayiassuidae 12,000 Mountain deer Odocoileus lucasi (was Navahoceros) Cervidae 13,000 Harrington s mountain goat Oreamnos harringtoni Caprinidae 12,000 Stout-legged llama Palaeolama mirifica Camelidae 11,000 Flat-headed peccary Platygonus (9 species) Tayassuidae 11,000 Pronghorn Stockoceros onusrosagris Antilocapridae 11,000 Saiga Saiga tartarica* Bovidae 12,000 Shuler s pronghorn Tetrameryx schuleri Antilocapridae 23,000 Proboscidea Gomphothere Cuvieronius hyodon Gomphotheriidae 12,500 American mastodon Mammut americanum Mammutidae 10,500 Columbian mammoth Mammuthus columbi Elephantidae 10,500 ~64 species listed Aves- Birds Woodward s eagle Amplibuteo woodwardi Accipitridae 12,000 American condor Breagyps sp Ca5thartidae 13,000 Dagett s walking eagle Buteogallus daggetti Accipitridae 13,000 Sea Duck Chendytes lawi Anatidae 2500 La Brea stork Cicona matha Ciconiidae ~13,000 California turkey Meleagris californica Meleagrididae 10,000 Errant eagle Neogyps errans Accipitridae ~13,000 Floridan hawk eagle Spizaetus grinnelli Accipitridae ~13,000 Merriam s Teratorn Teratornis merriami Teratornithidae 10,000 Teratorn Teratornis wooodburnensis Teratornithidae 11,000 *The two starred species are extinct in North America but still exist elsewhere (names many species, not all) This timeline runs from 12,000 years ago to about the year 2000.

4 Extinct North American Pleistocene Mammals Beautiful Armadillo Dasypus bellus Panamerican Ground Sloth Eremotherium laurillardi Ground Sloth Glossotherium robustum Panamerican Ground Sloth Eremotherium laurillardi Jefferson s Ground Sloth Megalonyx jeffersonii Shasta Ground Sloth Nothrotheriops shastensis Giant Short-faced Bear Arctodus simus Dire Wolf Canis dirus Scimitar Cat Homotherium serum American Lion Panthera atrox Sabertooth Cat Smilidon fatalis Mexican Horse Equus conversidens Yukon Horse Equus lambei California Tapir Tapirus californicus Vero Tapir Tapirus veroensis

5 Harlan s Musk-ox Bootherium bombifrons Yesterday s Camel Camelops hesternum Short-legged Llama Palaeolama mirifica Shrub Ox Euceratherium collinum Large-headed Llama Hemiauchenia macrocephala Stag Moose Cervales scotti Long-horned Bison Bison latifrons Gomphothere Cuvieronius hyodon American Mastodon Mammut americanum Columbian Mammoth Mammuthus comumbi Pygmy Mammoth Mammuthus exilis Woolly Mammoth Mammuthus prmigenius compiled by Dana Visalli/dana@methownet.com/

6 Mass extinctions of large mammals (and large birds) occurred on different continents and islands soon after humans arrived in those places. Graphic from The Diversity of Life by E.O. Wilson.