Paleontologists have advanced several theories to explain mammoths' rapid disappearance at the end of the last ice age, including meteors, diseases, climate change and human hunting. Evidence for meteor strikes has failed to materialize. As for human- or dog-borne diseases, experts say that it's hard to imagine a bug that could kill such a wide range of animals and only affect the large ones [sources: Lister and Bahn; UCMP]. That leaves climate and hunting.
As far as we know, mammoths could not live in areas akin to today's steppes, deserts, savannas or tropical forests, but were confined to the mix of plants peculiar to the mammoth steppe and parkland biomes. According to the climate hypothesis, that specialization may have doomed them to isolation and starvation. As the climate shift melted glaciers and raised sea levels, continents shrank and wetter conditions prevailed. Ill-adapted to such conditions, mammoth food sources dwindled, and mammoth populations declined with them [sources: Lister and Bahn; Mueller; Saey; Willerslev et al.].
Like the disease hypothesis, the overkill hypothesis emphasizes the fact that mammoths' shockingly fast decline coincides with the generally accepted arrival of humans in North America 13,300-12,800 years ago. It argues that big-game hunters, wielding spears with fluted, hafted Clovis points, hunted mammoths to extinction. Clovis points have been found with mammoth bones, and we know that humans used mammoth furs, meat and ivory. Moreover, we have found that both Neanderthals and Stone Age humans constructed buildings from mammoth bone [sources: Bower; Demay, Péan and Patou-Mathis].
But many questions remain. Given that many humans could have survived on a single mammoth, especially aided by natural refrigeration, and that early humans venerated the beasts in cave art, it's possible they treated mammoths with the reverence and restraint that Native Americans used toward buffalo [source: MGP]. Either way, hunter-gatherers likely had a varied diet and relied on small to medium game for meat, so how often they actually hunted mammoths (versus scavenging their remains) is unclear [sources: AMNH; Guthrie; Lister and Bahn].
Ultimately, the limitations of large mammals like mammoths, with their low birth rates and vast need for sustenance, might well have hastened their end, worsening the effects of isolation, habitat loss and predation, leaving only their dwarf descendants, cut off from the mainland on scattered islands, to carry on for another 6,000 years [sources: AMNH; Bower; Lister and Bahn; Nikolskiy and Pitulko].
Author's Note: How Woolly Mammoths Worked
Although the Pleistocene, with its climate wobbles and pulses of globe-spanning glaciation, might strike us as a fundamentally different sort of world than the one in which we live, the modern world is governed by the same forces and elements as the paleo. Now, as then, solar energy powers a complex, self-regulating climatological and ecological system that, though resilient, can rapidly collapse when pushed past a tipping point.
Whether mammoths were killed by hunters, by climate-driven starvation or some combination of the two is a question of much concern to their living cousins, the elephants, who once thundered across vast swaths of land and who today face human-driven habitat loss and poaching. The problem with tipping points is that they can move fast, have far-reaching impacts and quickly become virtually irreversible. The problem with allowing elephants to die, beyond the obvious tragedy, is that they are a keystone species in their ecosystems, potentially a kind of living tipping point. Their movements and activities create habitat for other animals and natural firebreaks, and their dung feeds numerous species, spreads seeds and provides soil nutrients. When an animal like that dies out, tipping point or not, it sends thunderous impacts throughout the ecosystem.
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