My son asked me that question right out of the blue one day. I think I might have been cooking dinner, and he just walks over and asks “why didn’t buffaloes go to heaven?” I’m pretty sure my answer was a largely unintelligible “unh?” Followed by some quick thinking – not to mention wondering if this was going to be a “do animals go to heaven” kind of question – and then a counter-question of my own. “What do you mean?”
Hey, they can’t all be winners.
He thinks about that for a moment. “Why didn’t they die when the others did?”
Others? Now I’m even more lost. What on Earth is he talking about?
“The saber-tooths!” he informs me. “Did they run away from the poisonous gas?”
And suddenly, it all clicks. He knows the dinosaurs went extinct, but he’s settled on the idea that it was poisonous gas that did them in. I think that comes from a dinosaur program we watched (I don’t recall which one) that showed a bunch of dinosaurs dying in a limnic eruption. So, he’s asking why dinosaurs didn’t go extinct when the saber-tooths did. Which is not a bad question at all.
Why did saber-toothed tigers go extinct?
At one point, it was a popular theory that saber-tooth cats went extinct because they were ‘superpredators’ that were too successful and wiped out their prey. After this, they starved. Recent studies, however, seem to contradict this. In Implications of Diet for the Extinction of Saber-Toothed Cats and American Lions, researchers examined wear patterns of teeth and jaws for animals recovered from the famous La Brea tar pits with those of living large carnivores. In tough times, our living large carnivores will put more effort into “bone consumption” – cracking and chewing bone for whatever nutrition can be obtained, and the research team believed it was reasonable to assume that extinct large carnivores would exhibit the same behavior. The results of the study?
DMTA here suggests that extinct carnivorans at La Brea may have utilized carcasses less than do some carnivorans today. This idea is inconsistent with interpretations of high incidences of tooth breakage in extinct Pleistocene carnivorans from La Brea compared with extant taxa. We suggest that tooth breakage data may be recording damage from both carcass utilization and prey-capture, with greater tooth breakage occurring due to increased prey size. Lower mean values for DMTA attributes consistent with greater durophagy (i.e., Asfc and Tfv) in both S. fatalisand P. atrox compared with both P. leo and C. crucuta, suggest that the late Pleistocene at La Brea was not any “tougher” (or perhaps “harder”) than the African savanna is today. Further, dental microwear texture comparisons through time offer no evidence that carcasses were utilized consistently more over time, especially for P. atrox. Thus, DMTA provides no support for the idea that prey-resources became scarcer over time. While competition with humans for prey is unlikely to explain the extinction of P. atrox and S. fatalis via competition for prey resources at La Brea, further work is necessary to assess the situation at other sites. Collectively, there is no evidence for greater carcass utilization during the Pleistocene; however, high levels of anterior tooth breakage could instead result from hunting megafauna and/or conspecific competition at La Brea. Thus, times may have been “tough,” but not as originally proposed.
So, what did kill them?
The Quaternary extinction
The Quaternary extinction is the name given to the mass extinction between 40,000 and 10,000 years ago. It impacted every continent to a greater or lesser degree, and in North America it rendered the majority of all animals over 44 kg (100 lbs) extinct. Nobody’s quite sure why it happened, but there are several hypotheses:
- Hunting: human predation wiped the megaherbivores out, and then the megapredators starved because they couldn’t eat enough prey to make up for the calorie count of hunting. Like all hypotheses it has supporters and detractors. The supporters point out a strong correlation between human arrival and extinction (particularly in Australia and New Zealand), while detractors point out that (for example) most of the North American megafauna were already extinct before humans are known to have arrived. Also (in North America) one megafaunal species that was a human prey species (bison) did not go extinct.
- Climate change: either an ice age or the end of an ice age drive the extinctions.
- Hyperdisease: humans and/or the animals travelling with them brought diseases that the local animals were not able to adapt to.
All of these arguments have multiple and ongoing arguments for and against them. The only clear scientific consensus is that the Quaternary extinction did happen. Barring some sort of smoking gun (aliens calling us and telling us they wiped out all the giant sloths, for instance), there will probably never be a clear consensus. My gut feeling is that it’s some mixture of predation and climate change and disease all hitting in some sort of extinction-level perfect storm, but that’s just me.
So, with apologies to my son, the better question might be “why didn’t the buffaloes go to heaven?” After all, North America lost 33 of 45 genera of large mammals – including wild horses, tapirs, camels, giant beavers, giant tortises, some really huge birds, and ground sloths. Why did the bison survive?
The answer is that they almost didn’t. Before the Quaternary extinction, there were five distinct species of bison in North America: the ancient bison (Bison antiquus), the long horned (or giant) bison (Bison latifrons), the steppe bison (Bison priscus), the American bison (Bison bison), and Bison occidentalis. The giant bison went extinct between 30 and 20 thousand years ago, during the Quaternary extinction. The ancient bison lived until about 10,000 years ago, and was the ancestor of the American bison, and the steppe bison went extinct around the same time. B. occidentalis went extinct around 5,000 years ago, and was most likely bred out of existence (DNA studies have demonstrated that they interbred with what became the American bison).
Of course, even after surviving the Quaternary extinction, they very nearly still went extinct. By 1900, they had been so extensively hunted that there were only 39 bison left alive in the United States, all residing in Yellowstone National Park. They’ve recovered with extremely careful management, but a population of 75,000 is a minuscule fraction of the pre-European bison population. So maybe the “hunting’ hypothesis for the Quaternary extinction isn’t so outlandish.