Unprecedented wave of large-mammal extinctions linked to ancient humans

Unprecedented wave of large-mammal extinctions linked to ancient humans
Statue of the Columbian mammoth housed at the University of Nebraska-Lincoln. A new study has found that such massive mammals were far more likely than their smaller counterparts to go extinct in regions occupied by ancient humans. Credit: Craig Chandler, University of Nebraska-Lincoln

Homo sapiens, Neanderthals and other recent human relatives may have begun hunting large mammal species down to size - by way of extinction - at least 90,000 years earlier than previously thought, says a new study published in the journal Science.

Elephant-dwarfing wooly mammoths, elephant-sized ground sloths and various saber-toothed cats highlighted the array of massive mammals roaming Earth between 2.6 million and 12,000 years ago. Prior research suggested that such began disappearing faster than their smaller counterparts - a phenomenon known as size-biased - in Australia around 35,000 years ago.

With the help of emerging data from older fossil and rock records, the new study estimated that this size-biased extinction started at least 125,000 years ago in Africa. By that point, the average African was already 50 percent smaller than those on other continents, the study reported, despite the fact that larger landmasses can typically support larger mammals.

But as humans migrated out of Africa, other size-biased extinctions began occurring in regions and on timelines that coincide with known human migration patterns, the researchers found. Over time, the average body size of mammals on those other continents approached and then fell well below Africa's. Mammals that survived during the span were generally far smaller than those that went extinct.

The magnitude and scale of the recent size-biased extinction surpassed any other recorded during the last 66 million years, according to the study, which was led by the University of New Mexico's Felisa Smith.

"It wasn't until human impacts started becoming a factor that large body sizes made mammals more vulnerable to extinction," said the University of Nebraska-Lincoln's Kate Lyons, who authored the study with Smith and colleagues from Stanford University and the University of California, San Diego. "The anthropological record indicates that Homo sapiens are identified as a species around 200,000 years ago, so this occurred not very long after the birth of us as a species. It just seems to be something that we do.

"From a life-history standpoint, it makes some sense. If you kill a rabbit, you're going to feed your family for a night. If you can kill a large mammal, you're going to feed your village."

By contrast, the research team found little support for the idea that climate change drove size-biased extinctions during the last 66 million years. Large and small mammals seemed equally vulnerable to temperature shifts throughout that span, the authors reported.

"If climate were causing this, we would expect to see these extinction events either sometimes (diverging from) human migration across the globe or always lining up with clear climate events in the record," said Lyons, assistant professor of biology at Nebraska. "And they don't do either of those things."

Off the face of the Earth

The team also looked ahead to examine how potential mammal extinctions could affect the world's biodiversity. To do so, it posed a question: What would happen if the mammals currently listed as vulnerable or endangered were to go extinct within the next 200 years?

In that scenario, Lyons said, the largest remaining mammal would be the domestic cow. The average body mass would plummet to less than six pounds - roughly the size of a Yorkshire terrier.

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

Lyons said that restructuring could have "profound implications" for the world's ecosystems. Large mammals tend to be herbivores, devouring large quantities of vegetation and effectively transporting the associated nutrients around an ecosystem. If they continue to disappear, she said, the remaining mammals would prove poor stand-ins for important ecological roles.

"The kinds of ecosystem services that are provided by large mammals are very different than what you get from ," Lyons said. "Ecosystems are going to be very, very different in the future. The last time mammal communities looked like that and had a mean body size that small was after the extinction of the dinosaurs.

"What we're doing is potentially erasing 40 to 45 million years of mammal evolution in a very short period of time."

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

Explore further

Researchers try to understand consequences of declining populations of large-bodied mammals

More information: F.A. Smith at University of New Mexico in Albuquerque, NM el al., "Body size downgrading of mammals over the late Quaternary," Science (2018). science.sciencemag.org/cgi/doi … 1126/science.aao5987
Journal information: Science

Citation: Unprecedented wave of large-mammal extinctions linked to ancient humans (2018, April 19) retrieved 18 September 2019 from https://phys.org/news/2018-04-unprecedented-large-mammal-extinctions-linked-ancient.html
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Apr 20, 2018
Nah, this is mostly story-telling. What is missing is the meat of the thing, namely HOW did they determine the history of extinction?
With the help of emerging data from older fossil and rock records, the new study estimate

Just what is this "help" and how was it used? One cannot come to a valid conclusion without that input. This article is just the story-telling part.

Apr 20, 2018
A different way of looking at this is from the biblical perspective:
Genesis 1:29 indicates that mankind was originally made as a vegetarian.
Then after the flood Genesis 9:3 mankind was allowed to eat animal flesh.
This of course also meant that mankind would be hunting animals for food.
Hence, for this reason the fear of mankind was put into all moving and creeping things:
Genesis 9:2
The fear of you and the terror of you will be on every beast of the earth and on every bird of the sky; with everything that creeps on the ground, and all the fish of the sea, into your hand they are given.

Now as for the extinctions - most large animals died in the flood in both stages - the rising waters and then the receding flow-off with the uplifting of mountains. This was when most animals were buried completely in sediment=>fossils.Then afterwards in the subsequent ice-age lots more of those that managed to breed and thrive from the rescue also died, e.g. the mammoths

Apr 20, 2018
A different way of looking at this is from the biblical perspective:

'A different way of looking at this is to be so stupid as to believe the ramblings of a bunch of bronze age peasants, who didn't know their arse from their elbow.' FTFY.

Apr 20, 2018
OH Crap!! We get blamed for everything! It was probably Fred Flintstones's dam pickup .

Apr 20, 2018
Fred says:
Gen1:29 indicates that mankind was originally made as a vegetarian.
Then after the flood Gen9:3 mankind was allowed to eat animal flesh.
This of course also meant that mankind would be hunting animals for food
And yet...

"Now Abel kept flocks, and Cain worked the soil. 3 In the course of time Cain brought some of the fruits of the soil as an offering to the Lord. 4 And Abel also brought an offering—fat portions from some of the firstborn of his flock." Gen4

-So according to god the 2nd gen of humans were herding animals. Irrespective of how these animals became domesticated or how Abel knew how to herd them, why on earth was he going to all that trouble if they weren't eating them?

Ok milk and eggs and wool and sacrifice. But it seems a stretch, no?

And why would they be going out hunting, which you must admit is dangerous and sweaty work, if they had flocks they could eat?

Unless of course they were hunter gatherers FIRST and became herders later.

Apr 20, 2018
Nothing in the bible holds water. Not even the flood.

The cain/Abel murder is by the way a vehicle to describe the age old conflict between growers and herders over land... Another indication of how overpopulation and the struggle for resources has been with us since humans first became able to hunt the animals that were keeping our numbers in check.

Was the flood gods solution to our tropical growth rate fred? Didnt work very well did it?

Maybe he could have just made us a temperate species like poor Neanderthal, and preempted a whole lot of misery and destruction.

But then we wouldn't have needed him would we?

Apr 20, 2018
@FreddyJoe, here's your New Clue™:

See that link at the end of the article? It's the link to the paper in the scholarly literature that the article is about.

Not that it will do you any good to read it; first you don't have the native intelligence to understand it, and second you'll dismiss it as another cretinist conspiracy theory about how all the siensetis hate jebus and the Babble by the drunken stone age sheep herders about the Super Magic Daddy In the Sky™ who gives you pie in the sky when you die.

Apr 20, 2018
Yeah, them there awful scientists... Hypothesizing novel ideas & then devising experimental methods to prove or disprove their speculations.

Then publicly announcing their verified conclusions. Without your permission.

The bastards! How dare they disregard your opinionated stuporstitious ignorance.

Still do not understand why you keep coming onto a science site to spout religious gibberish? Isn't even using the technological tools of satan, such as the computer. Endangering your immortified sole?

Of course one explanation is... You fairy-worshiping wackadoodles are masochists?

You furtively masturbate to online goat-porn? Than punish yourself with a combination self-flagellation and seeking the abuse of being jeered at in these comments?

Huh. Thought so.

Apr 20, 2018
mack, the article did cover the issue of size difference between African mammals and those located in Asia and the Americas.

The African mammals evolved alongside proto-humans and I'm guessing adapted to that predatory pressure.

African mammals are also smaller to deal with excessive heat. Such as that caused by being hunted. Fast and nimble are viable survival traits for prey.

Humans line-hunt as long-ranging predators. Similar to the Red Dogs. In a tropical climate rife with diseases and chronic misery of habitat.

Fire is the unmentioned weapon that advantaged human hunting. When the wind blows in the right direction, set the brush on fire and drive the larger, herd animals off a cliff or bluff or into a quagmire.

Groups of females and young were especially vulnerable to this method. Mass killing for a few pounds of meat. Extinction was inevitable for the Asian & American large mammals. They couldn't adapt or even breed fast enough.

Apr 21, 2018
Anyone who thinks Paleolithic man looked at a mammoth and thought "Gee, that's too much meat for my tribe to eat before it spoils, I think I'll hunt antelopes instead so I don't waste all that food" is an idiot.

Apr 22, 2018
Negates the many mass graves of wooly mammoths we've found that point to some sort of cataclysm but we often see this even today with game
The preferred way of hunting large animals was to drive them into killing zones using fire. Humans could kill them indiscriminately and harvest only the choicest meat.

As for smaller animals, hogs elucidate the problem

-Feral hogs are destroying crops and spreading disease at alarming rates. They are getting bigger and are assuming the role of bison in the American Midwest just as coyote are reverting to the wolves they once were.

Hogs ear bark and dig up roots and are capable of desertifying entire regions which is probably why the bible forbids them.

Apr 23, 2018
"...The great mammals in Africa survived well - so we can ask, why the large Pleistocene mammals weren't so lucky..."

An important reason large mammals survived in Africa is because the spear-thrower was never used in Africa. The spear-thrower ( called "atlatll" in Aztec and "woomera" in Australia) was used in Pleistocene Eurasia, Australia, and America. By itself a spear is not a good offensive weapon against an elephant. But with spear-throwers a band of stone-age hunters could attack and kill elephants in the open.

Apr 23, 2018
and these humans did not have the tools available to kill huge mammals in great numbers
All they needed was fire and a ravine or cliff to drive them into.

"Dr. Sauer has advanced the hypothesis
that the terminal Pleistocene fauna was destroyed by hunters making widespread
use of fire-drives in the pursuit of game.3 This weapon, he argues, would
have been far more effective, in terms of mass destruction, than the lance or
atlatl; Great body size in itself would have made the Pleistocene forms easy
victims to wind-driven fires, since the huge animals would have been lumbering
and unwieldly runners. Sauer deems it probable, furthermore, that the great
grasslands are of relatively recent origin, and that man-made fires have played
a major part since prehistoric times in the creation of circumstances favoring
the dissemination and evolution of the grasses."

-An old hypothesis but one that makes a lot of sense. Jarred Diamond also makes the case.

Apr 24, 2018
http://discoverma...nnection again....

Repetition is the mother of wisdom they say, because people have memory of tropical fish...
Is that why you have had 1000s of posts about dense aether deleted and dozens of sockpuppets banned?

'Cause in your case at least, repetition doesnt seem to be working out very well-

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