47.1D: The Pleistocene Extinction
- Describe the biodiversity loss associated with the Pleistocene extinction
The Pleistocene Extinction is one of the lesser extinctions and a relatively-recent one. It is well known that the North American, and to some degree Eurasian, megafauna disappeared toward the end of the last glaciation period. The extinction appears to have happened in a relatively-restricted time period between 10,000–12,000 years ago. In North America, the losses were quite dramatic and included the woolly mammoths (last dated about 4,000 years ago in an isolated population), mastodons, giant beavers, giant ground sloths, saber-toothed cats, and the North American camel, to name just a few. The possibility that the rapid extinction of these large animals was caused by over-hunting was first suggested in the 1900s; research into this hypothesis continues today. It seems probable that over-hunting was a factor in extinctions in many regions of the world.
In general, the timing of the Pleistocene extinctions correlated with the arrival of humans and not with climate -change events, which is the main competing hypothesis for these extinctions. The extinctions began in Australia about 40,000 to 50,000 years ago, 10,000 to 20,000 years after the arrival of humans in the area. A marsupial lion, a giant one-ton wombat, and several giant kangaroo species disappeared. In North America, the extinctions of almost all of the large mammals occurred 10,000 to 12,000 years ago, several thousand years after the first evidence of humans in North America. All that are left are the smaller mammals such as bears, elk, moose, and cougars. Finally, on many remote oceanic islands, the extinctions of many species occurred with the coincidence of human arrivals. Not all of the islands had large animals, but when there were large animals, they were lost. Madagascar was colonized about 2,000 years ago; the large mammals (prosimians) that lived there became extinct. Eurasia and Africa do not show this pattern, but they also did not experience a recent arrival of humans. Humans arrived in Eurasia hundreds of thousands to over one million years ago, after the origin of the species in Africa. This topic remains an area of active research and hypothesizing. It seems clear that even if climate played a role, human hunting was an additional factor in the extinctions.
Key Points
- The Pleistocene extinction in North America appears to have happened 10,000–12,000 years ago; this is several thousand years after the arrival of humans, who may have contributed to the extinction through hunting.
- Regions that experienced relatively-recent human arrivals show patterns of dramatic extinctions of megafauna hundreds to thousands of years after humans arrived; the same patterns are not observed in Eurasia and Africa as they did not experience a relatively-recent arrival of humans.
- To date, over-hunting by humans is one probable factor for the extinction of large mammals in the Pleistocene period.
Key Terms
- Pleistocene : of a geologic epoch within the Neogene period from about 2.6 million to 11,000 years ago; marked by the evolution of humans and the extinction of the large mammals
- megafauna : the large animals of a given region or time, considered as a group