How Long did it Take Humans to Wipe Out American Megafauna?

20 years ago, a computer simulation determined low levels of human hunting could cause the extinction of Pleistocene megafauna within a 1,640 year time frame. This simulation has held up well since the results were first published. A recent study of sedimentary data from Lake Llaviucu, Ecuador determined most of the megafauna in this region became extirpated 1,800 years after humans first entered the area. 1,800 years is remarkably close to 1,640 years. Another study, this one of a site in Patagonia, determined megafauna were extirpated in that region between 1000-2000 years after first human contact–also remarkably close to the computer simulation.

Locations of the data obtained for the below referenced study. Scientists dredged cores of sediment from beneath Lakes Llaviucu and Palicacocha in Ecuador. They used pollen composition, charcoal abundance, and dung fungus spore concentrations to determine the presence of humans, not environmental change, caused the extirpation of megafauna in this region. Image from the below referenced study by Raczka et. al.
Graph showing pollen composition, charcoal abundance, and dung fungus (sporomiella) concentrations. Dung fungus abundance is a proxy for the presence of megafauna; charcoal concentrations are a proxy for human presence because people set fires. People were present, but the environment did not change. It was a paramo grassland before people entered the region, and it still was a paramo grassland when megafauna became extinct in this region. Image also from the below referenced study by Raczka et. al.
Lake Llaviucu in Ecuador along with a llama. A glacial moraine dams a stream, thus creating this lake. Photo from Travel Ecuador.
A paramo grassland. Photo from the Missouri Botanical Garden. This region has been a paramo grassland for 16,000 years. Megafauna became extinct here about 12,800 years ago…1800 years after humans colonized the region. There was no change in the environment.

Scientists analyzed the pollen composition, charcoal concentration, and dung fungus spore concentration from a sedimentary core taken at Lake Llaviucu. The pollen composition provides information about the local environment. The area was under a glacier until ~18,000 years ago. After the glacier receded it was replaced by paramo grassland, an environment dominated by tussock grasses, rosette plants, and evergreen shrubs. Tropical cloud forests occur at lower elevations and plants from this environment contribute to the pollen rain. Charcoal concentrations are used as a proxy for human presence. Lightning strikes, a natural cause of fires, are extremely rare at this locality, so charcoal most likely came from human-set fires. Charcoal became common at this site about 14,600 years ago. Dung fungus spore abundance is a proxy for megafauna populations. Dung fungus declined in abundance 12,800 years ago. This is when populations of stegomastodons, horses, and ground sloths likely disappeared from the region. The core taken from this lake was 36 feet long and radiocarbon dates ranged from 16,200 years BP at the lowest part of the core to 9,000 years BP at the highest. The finding is consistent with similar studies at other sites in the Americas.

Lake Llaviucu is located in El Cajas National Park. Though most of the megafauna is gone, there are still some species of large mammals left here including llamas, mountain tapir, deer, spectacled bear, and cougar. The park is also home to 157 species of birds, and it is the Andean condor’s last stand. I’d love to visit the paramo grasslands and tropical cloud forests, but alas it is too far away.

Reference:

Alroy, John

“A Multi-Species Overkill Simulation of the End Pleistocene Megafaunal Extinction”

Science 292 (5523) 2001

Raczka, M. et. al.

“A Human Role in Andean Megafaunal Extinction?”

Quaternary Science Review 205 2019

Grayson’s and Meltzer’s Case Against Overkill would get Thrown out of a Court of Law for Perjury

I was listening to National Public Radio the other day, and they were interviewing a paleontologist who was excavating the bones of extinct Pleistocene megafauna. I didn’t catch his name or the name of the fossil site, but he was certain overhunting by humans caused the extinctions. For balance they also interviewed Meltzer, an archaeologists from SMU, who believes environmental change, not humans, caused the extinctions. About 20 years ago, he co-authored a series of illogical papers with Donald Grayson, an anthropologist, in an attempt to debunk the theory that man caused the extinction of Pleistocene megafauna. They are both a couple of dishonest shmucks. They are not paleo-ecologists. They are an archaeologist and an anthropologist. They know nothing about paleo-ecology. On the radio Meltzer simply repeated the same illogical arguments he made 20 years ago, and he ignored the overwhelming number studies that have since been published in support of an human role for the extinctions. A few years ago, Grayson published a book with a chapter about extinctions. He deliberately misrepresented the findings of a paper that ruled out environmental change as a cause of megafaunal extinctions. He suggested the results were the opposite of what the authors of the study concluded. (See: https://markgelbart.wordpress.com/2017/01/23/donald-graysons-disingenous-case-against-overkill/ ) In a court of law a judge will throw out a case, if a witness perjures himself. Grayson’s and Meltzer’s case against overkill would get thrown out for perjury. Incidentally, I informed Grayson of the above linked article. He refused to respond.

2 Responses to “How Long did it Take Humans to Wipe Out American Megafauna?”

  1. Jay Brodell Says:

    Bison are megafauna.

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