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Hunting was just final straw for mammoth, study finds

March 31, 2008
Courtesy Public Library of Science
and World Science staff

Does the hu­man spe­cies have mam­moth blood on its hands? Sci­en­tists have long de­bat­ed wheth­er cli­mate change or hu­man hunt­ing were pri­ma­rily re­spon­si­ble for con­sign­ing the shag­gy el­e­phant rel­a­tive to his­to­ry. 

Woolly mam­moths in an art­ist's ren­di­tion. (Cour­tesy Mau­ri­cio An­ton)
A new study uses cli­mate mod­els and fos­sil dis­tri­bu­tion to con­clude that the woolly mam­moth went ex­tinct mainly be­cause a warm­ing cli­mate, while hunt­ing was the fi­nal straw. 

It has been par­tic­u­larly hard to un­tan­gle these two po­ten­tial causes of ex­tinction, as cli­mate change and in­creased hu­man hunt­ing are linked, the re­search­ers said. When the cli­mate in mam­moth lands started to be­come too warm for the beast, this let hu­mans in­vade the ar­ea. There­fore, the mam­moth faced the heat and preda­t­ion pres­sure from hunt­ing in the same re­gions at about the same times. 

It had al­so been ar­gued that, as the mam­moth had sur­vived many pre­vi­ous tem­per­a­ture fluctua­t­ions, only hu­man hunt­ing that was a new con­di­tion se­vere enough to cause its de­mise.

Da­vid Nogues-Bravo of Spain’s Na­tional Nat­u­ral Sci­ences Mu­se­um and col­leagues claim to have set­tled the de­bate by us­ing math­e­mat­i­cal mod­el­ling to sep­a­rate the two fac­tors. They esti­m­ated cli­mate and spe­cies dis­tri­bu­tion at five dif­fer­ent times in mam­moth his­to­ry—ranging from 126,000 to 6,000 years ago—con­sid­er­ing tem­per­a­ture and rain­fall sim­ula­t­ions along­side the age and loca­t­ions of fos­sils. 

The re­sults show that the mam­moth suf­fered a cat­a­stroph­ic hab­i­tat loss, with the spe­cies 6,000 years ago rel­e­gat­ed to one-tenth of the hab­i­tat avail­a­ble to it 42,000 years ago, when glaciers were at their big­gest.

In fact, things were much worse for the mam­moth even ear­li­er, when high tem­per­a­tures al­so re­strict­ed its hab­i­tat 126,000 years ago, Nogues-Bravo and col­leagues ar­gued. At both these times, the cli­mate-related hab­i­tat loss would have forced the spe­cies to the brink of ex­tinction, they said. But the nail in the mam­moth’s cof­fin 6,000 years ago was that dur­ing the lat­er cri­sis, the mam­moth al­so faced ev­o­lu­tion­arily “mod­ern” hu­mans, spell­ing its doom.

The study is pub­lished in this week’s is­sue of the re­search jour­nal PLoS Bi­ol­o­gy.

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Does the human species have mammoth blood on its hands? Scientists have long debated whether climate change or human hunting were primarily responsible for consigning the shaggy elephant relative to history. A new study uses climate models and fossil distribution to conclude that the woolly mammoth went extinct mainly because of habitat loss due to a warming climate, while hunting was the final straw. It has been particularly hard to untangle these two potential causes of extinction, as climate change and increased human hunting are linked, the researchers said. When the climate in mammoth lands started to become too warm for the beast, this let humans invade the area. Therefore, the mammoth faced the heat and predation pressure from hunting in the same regions at about the same times. It had also been argued that, as the mammoth had survived many previous temperature fluctuations, only human hunting that was a new condition severe enough to cause its demise. David Nogues-Bravo of Spain’s National Natural Sciences Museum and colleagues claim to have settled the debate by using mathematical modelling to separate the two factors. They predicted climate and species distribution at five different times in mammoth history—ranging from 126,000 to 6,000 years ago—considering temperature and rainfall simulations alongside the age and locations of fossils. The results show that the mammoth suffered a catastrophic habitat loss, with the species 6,000 years ago relegated to one-tenth of the habitat available to it 42,000 years ago, when glaciers were at their biggest. In fact, things were much worse for the mammoth even earlier, when high temperatures also restricted its habitat 126,000 years ago, Nogues-Bravo and colleagues argued. At both of these times, the climate-related habitat loss would have forced the species to the brink of extinction, they said. But the nail in the mammoth’s coffin 6,000 years ago was that during the later crisis, the mammoth also faced evolutionarily “modern” humans. The study is published in this week’s issue of the research journal PLoS Biology.