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Unparalleled wave of outbreaks of large mammals associated with prehistoric humans



Homo sapiens Neanderthals and other younger human relatives may have started killing large mammal species – at least 90,000 years earlier than previously thought – to eradicate it, according to a new study published in the journal became science .

Biggest Best?

Elephant Dwarves woolly mammoths, elephant-sized ground sloths and various saber-toothed cats marked the collection of massive mammals that roamed the earth between 2.6 million and 12,000 years ago. Previous research suggested that such large mammals in Australia began to disappear faster than their smaller counterparts about 35,000 years ago ̵

1; a phenomenon known as extinction in the form of size.

Using new data from older fossil and rock records, the new study estimated that this extinction of size began at least 125,000 years ago in Africa. At this time, the average African mammal was already 50 percent smaller than on other continents, the study reported, although larger land masses can typically support larger mammals.

  Recovery of glyptodon in South American environment, next to megatherium or ground sloth. (CC BY-SA 3.0)

Restoration of Glyptodon in South American environment, adjacent to Megatherium or ground sloth. (19659007) CC BY-SA 3.0 )

Extinction followed human migration

But as humans emigrated from Africa, other large-scale extinctions began in regions and timelines that coincided with known ones Human migration patterns happen, the researchers found. Over time, the average size of mammals approached these other continents and then dropped far below those of Africa. Mammals that survived in span were generally much smaller than those that died out.

The size and extent of the recent extinction on the order of magnitude exceeded any other recorded in the last 66 million years, according to the study led by Felisa Smith at the University of New Mexico.

"It was not until the human impact became a factor that caused large body sizes to make mammals more susceptible to extinction," said Kate Lyons of the University of Nebraska-Lincoln, who led the study with Smith and colleagues at Stanford University and the University of Columbia authored University of California, San Diego. "The anthropological records indicate that Homo sapiens was identified as a species about 200,000 years ago, so it did not happen long after we were born as a species, it just seems to be something we do do."

"If you kill a rabbit, you will feed your family for one night, and if you can kill a large mammal, you will feed your village."

  Giant ground sloth (1965) right) and Glyptodon - Giant Armadillo (left) at the Smithsonian Museum of Natural History (CC BY 2.0)

Giant Sloth (right) and Glyptodon Giant Armadillo (left) at the Smithsonian Museum of Natural History. CC BY 2.0)

In contrast, the research team found little support for the idea of ​​climate change. For the past 66 million years, large and small mammals have been susceptible to temperature changes, the authors

"If As climate causes this, we would expect these extinction events to occur sometimes (diverging from) human migration around the world or always with clear climate events in the record, "said Lyons, Assistant Professor of Biology in Nebraska." And they do not do any of these Things. "

  A life depiction of Archie, a Colombian mammoth, is exhibited in the State Museum of the University of Nebraska in the Morrill Hall. Credit: Troy Fedderson, University Communications

A life-size exhibit of Archie, a Colombian mammoth, can be seen at the State Museum of the University of Nebraska at Morrill Hall. Credit: Troy Fedderson, University Communications

From the Ground

The team also looked ahead to investigate how the extinction of mammals could affect biodiversity. The question then came up: what would happen if the mammals now classified as endangered or endangered would die out within the next 200 years?

In this scenario, Lyons said the largest remaining mammal would be the domestic cow. The average body mass would drop to less than six pounds – about the size of a Yorkshire terrier.

"If this trend continues and all currently threatened (mammals) are lost, the flow of energy and the taxonomic composition will be completely restructured," said Smith, a professor of biology in New Mexico. "In fact, the size of mammals around the world will return to what the world looked like 40 million years ago."

  People hunt Glyptodon, by Heinrich Harder. (Public Domain)

People hunt Glyptodon, Heinrich Harder . ( Public Domain)

Lyons said the restructuring could have "profound implications" on the world's ecosystems. Large mammals are usually herbivores that devour large amounts of vegetation and effectively transport the nutrients around an ecosystem. If they continue to disappear, she said, the remaining mammals would play a bad role in important environmental roles.

"The types of ecosystem services provided by large mammals are very different from those obtained from small mammals," Lyons said. "The ecosystems will be very, very different in the future, the last time mammal communities looked and had a medium body size that was so small, it was after the extinction of the dinosaurs."

"What we do is potentially too Clear 40 to 45 million years of mammalian body size in a very short time.

Smith and Lyons authored the study with Jon Payne of Stanford University and Rosemary Elliott Smith of the University of California, San Diego received support from the National Science Foundation.

Upper picture: Several species of mammoths Earth went through during the Pleistocene epoch. CC of SA 2.0 )

The article " An unprecedented wave of large-mammalian extinctions associated with prehistoric humans was originally published on Science Daily

Source: University of Nebraska-Lincoln. "Unprecedented wave of large-scale extinctions related to prehistoric humans." ScienceDaily. ScienceDaily, April 19, 2018. www.sciencedaily.com/releases/2018/04/180419141536.htm

Reference:

Felisa A. Smith, Rosemary E. Elliott Smith, S. Kathleen Lyons, Jonathan L. Payne. Body size reduction of mammals in the late Quaternary . Science 2018; DOI: 10.1126 / science.aao5987


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