About 12,000 years ago, large mammals rapidly died out in North America. Mastodons, giant sloths and saber tooth cats were a few of the megafauna that disappeared. And it seemed to happen quite close to the time humans arrived on the continent.
Was it a coincidence or a cause?
"A big question ... is 'to what extent was it humans hunting these animals and what extend was it climate (or) environment changes ..?' I mean, there were major environmental changes,” said Isaac Ullah, professor of anthropology at San Diego State.
A study authored by Ullah and anthropologist Miriam Kopels described a computerized way to show how various factors cause an animal's demise. Call it an extinction calculator, if you like.
Parameters are plugged in to include hunting practices, populations, environmental conditions and some key facts about the animals. Kopels, who is a former student of Ullah’s, listed some other factors, such as how long it takes for the animal to reproduce or how much time it spends with its offspring, in addition to its lifespan.
“The animal's life history is a factor that’s going to contribute to its likelihood of extinction,” she said.
They run the computer simulation and it comes up with an extinction risk factor.
Environmental change and human interaction often combine to cause extinction.
For Kopels and Ullah, the test animal for the computer simulation was a South African buffalo, now extinct, called Syncerus Antiquus. Like so many animals worldwide, it died out at the end of the last ice age.
Ullah said climate change at the time was destroying and fragmenting the grasslands these grazing animals relied on. At the same time, anthropological evidence showed humans hunted the animals by targeting the less dangerous females and their calves.
When it comes to breeding the next generation, males are expendable, but if you kill off too many females? It's a problem.
“So it was the double sword of the humans' hunting methods and the fragmentation of their habitat due to climate change,” Ullah said of the Buffalo’s extinction.
Ullah said understanding the factors that lead to animal extinction is more important than ever, given the mass extinction that is occurring right now.
“Other than asteroids hitting the earth and that kind of stuff, this is one of the most severe, rapid extinction events, especially for large mammals around the world. They are dying off at an extraordinary rate,” he said.
Kopels said the value of their computer simulation device is its ease of use. She has even done demonstrations for children. And it could easily be used for modern animals that are endangered.
“So if I have an expert in conservation that wants to use this computer model, all they have to do is input some key factors about (the animal’s) life history and their environment, and they can just run it under these different circumstances,” Kopels said.
Kopels and Ullah co-wrote a paper on their analysis of the buffalo, Syncerus Antiquus, in the Quaternary Research journal.
