Passage
For decades, the sudden extinction of North America's Late Quaternary megafauna—including mammoths, mastodons, and saber-toothed cats—has fueled intense paleontological debate. One prominent school of thought, the 'overkill hypothesis' pioneered by Paul Martin, posits that the arrival of Clovis hunters around 13,000 years ago precipitated a rapid ecological collapse. Martin argues that large mammals, having evolved in the absence of human predators, lacked the necessary defensive behaviors, making them easy prey for highly efficient, coordinated hunting bands. This anthropogenic model highlights the correlation between human migration routes and the timing of extinctions.
Conversely, proponents of the climate change hypothesis contend that environmental shifts at the end of the Pleistocene epoch were the true drivers of extinction. During this period, the transition from the Last Glacial Maximum to the warmer Holocene was marked by extreme instability, altering vegetation patterns and disrupting established food webs. Advocates of this view argue that megafaunal species, adapted to cold steppe environments, were unable to survive the fragmentation of their habitats, pointing to historical climate cycles to demonstrate that extinctions occurred even in areas with minimal human presence.
A third, more controversial argument attributes the extinctions to an extraterrestrial event: the Younger Dryas impact hypothesis. This theory proposes that a comet or asteroid fragmented over the Laurentide Ice Sheet approximately 12,900 years ago. The resulting wildfires, shockwaves, and abrupt cooling, proponents argue, catastrophically disrupted the ecosystem. They point to geologic markers, such as carbon spherules and nanodiamonds in sediment layers, as evidence of a sudden, continent-wide disturbance that simultaneously decimated both megafaunal populations and the Clovis culture itself.
Question
Based on the passage, match each scientific hypothesis regarding the Late Quaternary megafauna extinctions with its corresponding central argument.
- Overkill hypothesisEcological collapse was initiated by the sudden introduction of a novel predator species to which native fauna were unadapted.
- Climate change hypothesisRapid shifting of glacial boundaries led to the fragmentation of critical habitats and altered vegetation structures.
- Younger Dryas impact hypothesisA cosmic event caused immediate environmental devastation and a sudden thermal shift that disrupted habitats and human populations.