Megafauna Extinction

Miscellaneous and Personal Stuff I Must Share
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A new study has confirmed the primary cause of megafaunal extinctions that occurred (mostly in North America) around 10000 years ago.

Altho the so called Overkill Hypothesis had been soundly debunked decades ago*, scientists have since then been debating whether it was climate change, human intervention (burning or hunting or introduced species), disease or some other culprit.

Now a recent article has shown that climate change was the primary culprit, altho no doubt aided by hungry humans, etc.
https://www.nature.com/articles/s41559-017-0125.epdf?referrer_access_token=uDrrXWo5-5l9fHm9IY_W-dRgN0jAjWel9jnR3ZoTv0PaK4aqrQ-d59og4YuZKC2XUx-tc4CXT202sPg5epBHhJ50LEHpAqMTBj4_1Y6TwQNqP91AqMbaKdM4xssEu5NUb2TLfVq_6xM4nJJtsgFJ3L84HeOkTJgpxS3k7aCWoJqGzsthhboicHcBbsJ5CEoa1gapqq0-gOHZPyRy5l08w9KK-a5w3WeIQ-fL7wvZeMXJDC04OIvTq_zOMvyaqd_VPDejAYR7SP1pBHKHKLeqtA%3D%3D&tracking_referrer=www.newsweek.com

*http://www.amnh.org/science/biodiversity/extinction/Day1/overkill/Bit3.html

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Moderator Action

I don’t see a question here.

Moving thread from GQ to MPSIMS.

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Has there ever been a natural mass extinction that climate change was not the major factor?

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Well, maybe we’re starting one, but there- climate changes is a factor too, in a way.

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Articles trying to absolve humans of the North American Megafauna extinction appear with some regularity. Comet strike, superbug, volcanic eruption etc. What they all have in common is pretending the extinctions happened at the same time across the Americas.

As opposed to you know, happening when humans got there. Mammoths lasted till 1700 BC, untill humans got to the last refugia. Ground slots outlived other American megafauna by 5 000 years, until humans got to the Caribbean islands.

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But you see- the time “when the humans got there” has been adjusted many times, each time earlier.

The Overkill Hypothesis- for which there is no evidence at all- postulated that the megafauna extinctions occurred about 10000 years ago- when Archaeologists thought humans had arrived.

But now that date is more like 14000 years ago and quite possibly later.

Of course, it is possible that humans did kill off the last few (300 maybe?) mammoths on Wrangel island- but there is no evidence of mammoth hunting. In any case, that was a isolated population.
https://www.nytimes.com/2017/03/02/science/woolly-mammoth-extinct-genetics.html?_r=0
*The dwindling population during this 40,000 year period suffered a reduction in genetic diversity of some 20 percent, the Swedish team reported, suggesting that the lesser fitness of the Wrangel mammoths might have contributed to their extinction.

In fact, the Wrangel mammoth’s genome carried so many detrimental mutations that the population had suffered a “genomic meltdown,” according to Rebekah Rogers and Montgomery Slatkin of the University of California, Berkeley. Analyzing the Swedish team’s mammoth data at the gene level, they found that many genes had accumulated mutations that would have halted synthesis of proteins before they were complete, making the proteins useless, they report Thursday in PLOS Genetics*.

The earliest settlement date of North America, until now estimated at 14,000 years Before Present (BP) according to the earliest dated archaeological sites, is now estimated at 24,000 BP, at the height of the last ice age or Last Glacial Maximum

Correlation does not imply causation- especially where the correlation is not really there.

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Great username/thread title combo [d&r]

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Asteroid strike that killed the dinosaurs. Unless you want to argue that the asteroid caused climate change which killed the dinosaurs.

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Can you quote the part of the Nature article that says that?

As do posts by he OP.

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Just the other day I read this article in the Atlantic. On my somewhat casual reading, it seemed to present several factors supporting the human role in megafauna extinction.

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There is some correlation and humans probably contributed to the end of species, but species already on the decline and quite likely disappearing even without human intervention. Even the last few mammoths and other species may not have been killed by humans, those final survivors could have been living in very remote locations. Humans probably did contribute to the end of some species in some local areas, but still not due to overkill, just because the populations were already in decline. Human predators, among others certainly were a factor in the complex web of interactions that lead to extinction, it’s just an ‘overkill’ of another kind to conclude our ancestors were the deciding factor, just as blaming climate change is. And ‘overkill’ hasn’t been the complete story presented that I know of, we’ve been aware of great environmental change with the retreat of great glaciers and many changes in the environment accompanying in that time whether directly related to the warming period or not. I think human ego has contributed to the idea of ‘overkill’ portraying ourselves as mighty hunters capable of wiping out monstrous species. Until modern weapons arose we were much better at killing off species in limited environmental niches not the ones capable of roaming over vast reaches of the continents.

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1638: Humans establish a permanent settlement on Mauritus. Extinctions of the larges native species follow, the Coot in 1667, the Dodo in 1662.

1250-1300: Humans arrive in New Zealand, Megafanuna extinctions follow.

350-550 : Humans arrive on Madagascar. Megafauna extinctions follow.

1700 BC: Humans arrive on Wrangel Island. Extinction of the mammoth follow.

4 000 - 5 000 BC: Humans arrive on the Caribbean Islands. Megafauna extinctions follow.

ca. 14 000 BC: Humans arrive in the Americas. Megafauna extinctions follow.

ca. 55 000 BC: Humans arrive in Australia. Megafauna extinctions follow.

Also see places like Crete, Sardinia, Cyprus etc.

The fact is, when humans come to a place with animals that do not fear humans, we hunt them to extinction. This is not news, it has happened regularly and well into historical times. Any explanation that claims to show that the Americas was the big exception would need to demonstrate why the first settlers behaved in a manner so extremely different from every other human population hitting a virgin territory.

These were all populations that have managed to survive through a vast number of climate swings, sometimes extremely large ones such as ice ages and interglacials before, with little evidence of stress. And the number of additional factors you need to invoke to explain these things without humans causing it multiplies hugely with every new set of extinctions you need to explain away.

Yes, sometimes it takes a while. Especially in large locations where humans have to learn and adapt a bit, and where refugias can exist for a while. But we learn faster than creatures evolve, at least the big ones with large generation times. Hence, the tendency in these extinctions for larger -mega- fauna to be hit hardest.

And when you have new waves of humans with improved hunting techniques arriving… well look at the Tasmanian Tiger, the Great Auk or the Passenger Pigeon.

Like I said, this is an entirely historically attested phenomenon.

The one continent that kept most of its megafauna is the one where it grew up with us. Africa.

Yes, the Wrangel Island Mammoths had genetic problems. They were an exceptionally small and inbred population because mammoths were dead everywhere humans lived!

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The notion that stone-aged humans on foot were able to hunt down and kill every last horse on the entire North American continent does seem a little preposterous … especially since humans apparently were not able to do this on the Asian continent in spite having a far longer time to do so …

Whatever happened … what evidence is there that humans themselves were unaffected?

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The thing is, humans entered the Asian continent much. much earlier, with a lower level of hunting tech. So the big animals had more generations to get used to us. Later arrivals were in more virgin territories, and were more similar to a “blitzkrieg”, or an invasive species.

As for how, exponential growth.

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Right there in the bolded summary.

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Dodo? Not hunting:wiki* At the same time, humans destroyed the forest habitat of the dodos. The impact of the introduced animals on the dodo population, especially the pigs and macaques, is today considered more severe than that of hunting.*

Yes, because America is a continent and the rest are mostly small islands with limited populations, already strained by their environment, such as the Wrangel Island Mammoth.

And again the timing is off:
http://www.sciencemag.org/news/2014/01/what-killed-great-beasts-north-america
Boulanger and Lyman compiled databases of radiocarbon dates from both megafaunal finds and Paleoindian sites for the northeast, throwing out any dates whose reliability had been or could be questioned. This gave a final sample of 57 megafauna dates from 47 different sites and 25 Paleoindian dates from 22 sites. When the two databases were compared, it became clear that most of the megafauna had already disappeared before humans came on the scene—suggesting that the humans had little to do with their demise.The radiocarbon dates also suggest that northeastern megafauna underwent two major declines before finally going extinct. The first was 14,100 years ago, before any humans were in the region, but the number of animals then recovered after about 500 years; the second and final population crash began 12,700 years ago, when Paleoindians had just arrived in the region, according to the archaeological record. Moreover, the team reports in the 1 February issue of Quaternary Science Reviews, even though humans and megafauna continued to coexist for about 1000 years before the animals finally went extinct, the animals were already on their way out: Between 75% and 90% of the northeastern megafauna were gone before humans ever came on the scene. Yet even during the millennium of human and animal overlap, the team argues, there is no evidence for hunting: Neither megafaunal nor Paleoindian sites in the northeast contained animal bones that were butchered or otherwise modified.

Here’s the thing: species of land megafauna, since say 1700, only a darned few have gone extinct. And that’s with machine-guns and a population several orders of magnitude greater. Yes, in the last few decades we have made efforts to conserve them. But if a few hundred thousand guys with spears could make extinct hundreds of major species of land megafauna, how come 100 million guys with guns have barely managed a few?

And, science requires this thing called "evidence’ not just a few maybe possible strained coincidences. No evidence of hunting for the Wrangell island mammoth. To count the number of mammoth kill sites (each with one or a couple of kills) in all of North America I wouldnt have to take off my shoes.

But compare that with Europe, with many kill sites, some with perhaps tens of thousands of kills.* Evidence. *

Correlation does not imply causation- especially where the correlation is not really there.

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Nice guess, but where’s the evidence? In areas with no hunting, yes, deer can almost be walked up to. But they get shy in one season.

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The article in *Nature *says nothing of the sort. I knew that without reading it, because:
[ol]
[li]That’s not how science works[/li][li]The authors are well-established non-hacks[/li][li]The editors and peer reviewers of a high-profile journal are unlikely to let such a comment fly.[/li][/ol]

And having tracked down the article, since the link didn’t work on my phone (it’s DOI 10.1038/s41559-017-0125), the authors do not weigh their climate change analysis against other hypotheses.

The data and their analysis are consistent with extinctions lining up with increased moisture around deglaciation events leading to a boon of quality forage, followed by a spread of herbivore-resistant plants that need more water.

I have no dog in this debate, but let’s leave the sensationalist headlines to the so-called science journalists.

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:rolleyes::rolleyes::rolleyes:

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Yes, your OP was obviously false without having read the paper. I did, however, read it in its entirety before posting. Did you? You were asked to back up your OP over eight hours ago and all you have to offer is “the bold part.”