New Theory on N. Am. Extinctions


#1

Ai dont know how recent this is, but ai read it in the newspaper this morning. Aparently, teams of scientists have found a layer of soil containing microscopic diamonds that could only be created from a meteor impact - spread out across north america. Oh, did ai forget to mention that these diamonds come with a black layer dated to about 13000 years ago at the start of the Younger Dryas (people call it a small ice age, or something like that)?
The researchers speculate that an impact must have caused the mega-mamal extinctions that happened - exactly at that time! (well, within 100 or so years of the supposed impact) Also at that time, the then dominant Clovis people underwent a massive population reduction and did not return to the Great plains and some other regions for hundreds of years.
Ai just found this from the Chicago Tribune: http://www.chicagotribune.com/news/local/chi-comet-webjan02,0,3624054.story


#2

Off topic, directly, but on topic overall… I’ve been thinking a lot lately about the Pleistocene Extinction and the various theories.

http://en.wikipedia.org/wiki/Quaternary_extinction_event#The_Pleistocene_or_Ice_Age_extinction_event

I recently attended a talk by an archaeologist on the populating of the Americas by humans. Very interesting talk that covered many of the oldest sites found around the continents. However, he kept mentioning the extinction of the megafauna was caused by humans. This was annoying to me, as I’ve read a bit of other theories and they make more sense to me. Ian (woozletracker) posted this quote by George Monibot:

Had the Mesolithic people of the Americas eaten everything they killed , they would scarcely have trimmed the herds of game, so small were their numbers. One ground sloth could have fed a clan of hunters for months. The speed with which the megafauna of the Americas collapsed might suggest that they slaughtered everything they encountered. Among those who broke into the New World, anyone could be a Theseus or a Hercules: slaying improbable monsters, laying up a stock of epic tales to pass to their descendants. [...] Perhaps the care with which some indigenous people of the Americas engage with the natural world came later. (p.138)

I’m like… Perhaps if you didn’t just assume that humans are idiots, you would look at other models.

The idea that humans would waste food like that baffles me. No wild animals waste food in a manner, and I don’t see “wild” humans doing that either. Their intelligence and “care” with which they engage the natural world did not come later.

“So although we can say for sure that humans did hunt them, it would be quite a leap to say that they did so to such an extent that caused them to become extinct - at most it would have been the final straw.”
[url=http://www.telegraph.co.uk/science/evolution/10301194/Climate-change-killed-the-woolly-mammoth-researchers-claim.html]http://www.telegraph.co.uk/science/evolution/10301194/Climate-change-killed-the-woolly-mammoth-researchers-claim.html[/url]

Anyone have some good sources on this?


#3

Checking the book again, I see Monbiot references Paul S. Martin’s ‘Twilight of the Mammoths’ (2005 - the inventor of the ‘overkill’ theory still selling his wares…) and a 2006 review by Koch & Barnosky, ‘Late Quartenary extinctions: state of the debate’ from the ‘Annual review of ecology, evolution, and systematics’. It’s online here behind a paywall / library subscription, but here’s the abstract:

Between fifty and ten thousand years ago, most large mammals became extinct everywhere except Africa. Slow-breeding animals also were hard hit, regardless of size. This unusual extinction of large and slow-breeding animals provides some of the strongest support for a human contribution to their extinction and is consistent with various human hunting models, but it is difficult to explain by models relying solely on environmental change. It is an oversimplification, however, to say that a wave of hunting-induced extinctions swept continents immediately after first human contact. Results from recent studies suggest that humans precipitated extinction in many parts of the globe through combined direct (hunting) and perhaps indirect (competition, habitat alteration) impacts, but that the timing and geography of extinction might have been different and the worldwide magnitude less, had not climatic change coincided with human impacts in many places.

So right away it doesn’t seem to fit Monbiot’s strong assertions that ‘it was not, as many paleontologists supposed, primarily climate change that wiped out the American megafauna […] They were hunted to extinction. […] they probably stood and watched, without fear, as the hunters approached.’ (‘Feral’, p.138) More recently he’s been citing the work of Chris Sandom and others who spoke at the Oxford Megafauna Conference - see this hysterical article from last March, or bypass and go straight to Sandom’s paper, summarised here.

Humans versus climate

Sandom and his team gathered records on individual species known to have gone extinct between 132,000 years ago (at the beginning of the last interglacial period) and 1,000 years ago. They focused their analysis not on the continent level, as many studies have, but country-by-country or even state-by-state, in large nations like the United States. All told, the researchers analyzed 177 extinct mammals that had weighed more than 22 lbs. (10 kilograms).

The researchers then compared the timing of the extinctions with changes in climate and precipitation, and with human migration.

“What we found was, in sub-Saharan Africa, you’ve got the least extinction,” Sandom told Live Science. “In Eurasia, you’ve got the next-least.” [Wipe Out: History’s Most Mysterious Extinctions]

This fits the human-hunting hypothesis well, he said. Large animals in sub-Saharan Africa would have had millions of years to co-evolve with humans as they learned to use tools. When early humans moved into Europe and Asia with their primitive hunting methods and weapons, they would have had access to a new population of animals unaccustomed to their clever ways.

In Australia and the Americas, where humans arrived comparatively late, the extinctions were the most extreme, Sandom said.

“You’ve got this very advanced hunter arriving in the system,” he said, not unlike the invasive species that cause native extinctions today. The researchers did not find a strong overall relationship between extinctions and climate, except in Eurasia, Sandom said. Climate there might have interacted with human arrival in a complicated way, with temperatures determining where people migrated, he added.

Overall, humans’ arrival was responsible for 64 percent of the variation in extinction rates around the globe, while temperature changes explained 20 percent of the variation, mostly in Eurasia.

Climate change can stress animals, Sandom said, but climate variations do not always spell doom for species — animals may simply alter or restrict their range in order to find a habitat that sustains them. Humanity may have disrupted this adaptive process for large mammals, he said.

“That was the final straw,” Sandom said. “They couldn’t handle the new predator turning up.”

Not sure I buy every aspect of it - some of his wording is very silly and shows the usual lack of understanding about hunting cultures - but there it is. Certainly more measured and qualified than Monbiot’s ridiculous macho-hunter-kill-everything-in-sight depiction!

I’d be interested to see your sources and/or other theories. I’m aware of the guy quoted in ‘Endgame’ (second book from p.541), Eugene S. Hunn, with his ‘this beast, like dracula, will not die’ debunking and Jensen’s native american friend pointing out the racist subtext, but it would be good to see this updated in response to the newest wave of research.

cheers,
I


#4

Hey Ian,

This is great info!

It makes sense as laid out up there. The thing that bugs me about Monibot is his assertions of waste. No wild animals waste their food. “Wild” humans are wild animals. I think for energy efficiency, they don’t waste food. So who knows. They most likely contributed to the megafauna extinctions, but I doubt they wasted their food. They used to think the Mammoth kill sites were from a giant stampede but after dating bones they realize these sites were used for hundreds of years… Not sure where I read that. :frowning:

I’m going to link Jason Godesky to this thread because I think he might have some other resources on the topic.


#5

I’m working on an article on “Tending the Wild” for the rewild.com main page and this quote from Nancy Turner came up that I thought related to the conversation:

“Ecological restoration is a process, a directed action aimed at repairing damage to ecocultural systems for which humans are responsible. Environmental degradation has impaired the functioning of both ecological and cultural systems and disrupted traditional practices that maintained these systems over several millennia. Indigenous and local peoples who depend on the integrity and productivity of their immediate environments more than the global, urbanized society are directly affected by ecosystem damage. Conversely, ecosystems have become further diminished in the absence of the cultural practices that once sustained them. Despite this clear connection between cultural and ecological integrity, however, the knowledge and interests of indigenous peoples typically are not considered in attempts to restore degraded ecosystems.” - Nancy Turner, Restoring the Pacific Northwest. Traditional Ecological Knowledge and Restoration Practice pg. 393.


#6

Hi Peter,

Yes, the food waste allegation seems dodgy. ‘Extraordinary claims require extraordinary evidence’ as the saying goes. Monbiot (not ‘Monibot’ btw :slight_smile: ) has provided a theory, but evidence to support it is incredibly thin. I don’t know how you could even attempt to prove something like that, this far removed from their immediate circumstances.

Not sure it’s exactly true that ‘no wild animals waste their food’. What about surplus killing? Predators like foxes, wolves, stoats etc. will opportunistically kill more prey than they require for immediate sustenance if they happen to be in a situation where that’s possible and the additional risk or effort isn’t too great. Sometimes they will cache the other carcasses for a later date, other times not - in which case other scavengers or even just bacteria & fungi come in to take care of the ‘waste’. It occurs to me that human hunters might have done this too (possibly they still do in some ways, I don’t know). One prehistoric case that people have seized upon in Europe is the discovery of loads of horse carcasses buried around the Solutre rock in France (see here). The first researchers thought that Mesolithic hunters were driving whole herds off the top of it to fall to their deaths, but this has been revised to the theory that they were trapped and killed by the side of the rock. Apparently they didn’t make full use of the carcasses:

The vast number of individual horses, many articulated remains, the scarcity of butchery evidence and the lack of evidence of transportation of skeletal elements away from the sites suggested that large numbers of horses were killed at any one time and that their intact carcasses were not fully exploited. The minimal butchery may reflect the way in which the horses were hunted. It is suggested that the horses were ambushed as they followed a migratory trail. Hunters would have killed as many horses as possible before the herd panicked and took flight. This method would have produced many carcasses, from which perhaps only a few were selected for further processing.

Possibly this was due to their abundance especially in the summer months. They also found a smaller number of reindeer and bison carcasses, with the reindeer showing ‘more intensive evidence of butchery, indicative of full utilisation of their carcasses’ - perhaps due to the fact that they were ‘hunted in winter and spring’ when other game would have been scarce. Either way the concept of ‘waste’ - which comes with some very civilised assumptions - perhaps shouldn’t even come into it, because whatever the human hunters didn’t eat became available for the rest of the community:

carnivores also utilised the carcasses extensively and were probably responsible for the destruction of some elements, e.g. the sacrum. This is interpreted as the opportunistic scavenging of the remains of animals killed by Magdalenian hunters, although the intensive gnawing means that the possibility of some carcasses by carnivore kills cannot be ruled out.

Like that Nancy Turner quote a lot. It points to all the things overkill theorists are missing by ending their discussion of prehistoric h/gers at ‘they caused mass extinctions’. Well maybe, but what happened next? How come there’s such a strong correlation between areas of high biological diversity with the presence of indigenous people?

W.W.F. has devised a new approach to its conservation work called Ecoregion-Based Conservation (E.R.B.C.). In developing this approach, it has mapped out 874 ecoregions of the world, and has found 238 of them to be of the utmost importance for biodiversity.

In collaboration with the international N.G.O. “Terralingua: partnerships for linguistic and biological diversity”, W.W.F. carried out an exercise to map all identifiable indigenous and ethnolinguistic groups of the world on the G200 map. The results show a very significant overlap of the biodiversity-richest areas of the world with high concentrations of distinct cultures. (http://www.terralingua.org/blog/2000/07/16/indigenous/)

I have a slight quibble, though, with Turner’s point about how ‘ecosystems have become further diminished in the absence of the cultural practices that once sustained them’. Isn’t ‘diminished’ a subjective term here? I only mention it because conservationists over here use similar arguments as a kind of claim to virtue for the reinstatement of old farming practices which created heathland and wildflower meadows for the use of livestock from what used to be forest, wetland or other ‘unproductive’ land. Likewise coppicing in woodland is justified on the grounds that it ‘increases biodiversity’ because of more sunlight reaching the woodland floor, leading to more flowering plants, butterflies etc. But then this comes at the expense of all the species who depend on the exclusion of light and the consequent damp, dark environment provided by a thick tree canopy. These are apparently now the most threatened species in Britain due to largescale loss of habitat:

High diversity of habitat is clearly an undesirable general goal: the costs and benefits depend on the scale of the habitats. A diverse park or garden may have more landscape or educational appeal than a dense, dark oak or spruce monoculture, and more species of vascular plants - but more specialist, vulnerable, and globally rare species could inhabit the woodland. Mud and sea lochs may not be diverse, but are important habitats.

Coppicing, which turns woodland into glorified scrub, is again a useful example. It is often thought to increase habitat diversity since the rotational cutting of patches of the coppice woodland gives an impression of variety. However, this may be an artefact of the way people see habitats: fractal geometry shows that architectural diversity is scale-dependent, and to many organisms there may be more habitat diversity in a mature woodland although it may seem homogeneous to an animal as large as a human. The smaller the organism, the greater the rate of loss of habitat as felling occurs. A large late-successional habitat, such as a forest with natural treefall gaps, will often have a high habitat diversity - with both very high species richness and quality.

To saproxylic organisms, species requiring large or complex structures, or abundant foliage, coppicing does not increase diversity. Sterling and Hambler (1988), and Waring (1988) have found coppicing damaging to woodland spiders and moths. It may benefit butterflies like the Pearl-bordered and Heath Fritillaries, Boloria euphrosyne and Mellicta athalia . However, such butterflies have alternative habitats on woodland edges, rides, and even on grasslands and heathlands respectively (Thomas 1986). Is it ethical to ‘diversify’ or create habitat for them at the expense of the woodland species such as the epiphytic ‘lower’ plants - the true natives of much of our landscape, with nowhere else to go except extinction?

I feel like there’s a difference between this and ‘tending the wild’ scenarios but I’m not sure what it is.

Would be interesting to hear Jason pitch in again :slight_smile:

best,
I

PS the main site is looking great already - good job!


#7

That’s very interesting about the excess caching and the concept of “waste” being a civilized thought.

The excess caching reminds me of the book “People of the Deer” in which the native of central northern Canada would basically kill as many deer as they could while the deer migrated through their region, 3 times a year, and then cache it for the times in between. I wonder how much they ate, or how much of their caches were spoiled. I still think that small bands of hunter-gatherers wouldn’t be killing huge amounts of animals to cause a “die off” but then again, anything is possible and the evidence and ideas you are showing here are really good and make sense.

That linguistic information is incredible!!!

I understand the quibble with Nancy Turner’s quote. She probably addresses that more specifically in her book. I’m re-reading it as I work on the article Tending the Wild for the main rewild.com page. Are you interested in helping us write any of the main articles? I think your knowledge and research and sources would really help.


#8

Yeah, you can only ‘waste’ something that you’ve claimed total ownership over and denied the rights of access to anybody else, to the point where you forget that they even exist. I catch myself thinking this way about the veg growing (sometimes ‘the veg I’m growing’ - what hubris!) on my allotment patch all the time: ‘Oh there’s too many courgettes for me to make use of, I’m going to have to throw some of them away. What a waste!’ or ‘The bloody fox got to my corn just as I was getting ready to harvest it. All that effort gone to waste!’.

Interesting about the people of the deer. I wonder does killing ‘as many deer as they could’ mean a lot more than they would conceivably need, even as insurance, or did they get to a cut-off point where they recognised that enough was enough? Would be interesting to know if their population went through boom and bust phases along with food availability like D.Quinn’s theory suggests.

I still think that small bands of hunter-gatherers wouldn't be killing huge amounts of animals to cause a "die off" but then again, anything is possible

Well, surely not on purpose - why exterminate your own food supply? The thing that struck me about the Solutre situation is that the horse remains had built up over thousands of years (‘The bone-laden magma can be explained by the fact that the site was used by four great paleolithic civilizations [sic] over the 25,000 years from 35,000 to 10,000 B.C, an extremely long time period.’ - wiki). So yes, they killed a bunch of them, possibly more than they needed then & there, but the horses kept coming back, choosing to follow the same migration year after year, generation after generation. What does that tell you?

[center][/center]

Keep meaning to read Nancy Turner after your recommendations in various places. I wish there was something similar available for indigenous cultures in Europe :frowning:

Are you interested in helping us write any of the main articles? I think your knowledge and research and sources would really help.

Yes, that could be fun - which one(s) did you have in mind? I’m not really that scholarly though - it’s mostly just clicking through from the citations on wikipedia articles. Force of habit from uni days :wink:

cheers,
I


#9

Re: “waste”: Peter, wasn’t there a bit of talk about wolves caching large kills in Wolf Totem?

All the things folks have said here are good. I’ve found it quite ridiculous how much people try to simplify the Pleistocene die-off down to one brute cause. Ecosystems are complex places. When you introduce an apex predator (and a ridiculously well adapted one, like humans, who also happens to be omnivorous) to a system (especially if that system is virtually devoid of mammals, like New Zealand was before human arrival), OF COURSE there is going to be dramatic change. And if you mix that with drastic changes like the end of an ice age, OF COURSE there is going to be dramatic change.


#10

Woozletracker, re the horses in Solutre… the problem with the argument is, well, yes, for thousands of years, they kept killing the horses, and the horses still kept coming. And then, fewer came. And then, they didn’t come, perhaps. And Solutre was done for. Intensification will do that, no matter how long it takes…


#11

As far as I know it’s still an open question why the horses stopped migrating past Solutre. Not that I’ve read any in-depth scientific study of its prehistory… Equally ignorant about herd migrations but I can think of dozens of potential reasons for the yearly patterns to shift over time (eg: changes in food availability, decreased desirability of the destination, obstacles forcing a change of path, overarching warming or cooling trends etc. etc.) What convinces you that there was an intensification of hunting, and that this led to their local demise?

Welcome back :slight_smile:
I


#12

Peter , I recently wrote an article on our Dirttime site called “Tending your own Wilderness” … might be of interest …

Dude


#13

[quote=“woozletracker, post:11, topic:1265”]As far as I know it’s still an open question why the horses stopped migrating past Solutre. Not that I’ve read any in-depth scientific study of its prehistory… Equally ignorant about herd migrations but I can think of dozens of potential reasons for the yearly patterns to shift over time (eg: changes in food availability, decreased desirability of the destination, obstacles forcing a change of path, overarching warming or cooling trends etc. etc.) What convinces you that there was an intensification of hunting, and that this led to their local demise?

Welcome back :slight_smile:
I[/quote]

Youz right. I am just speculating. But generally, the late ice age cultures in the rich refugia in Europe were intensifying cultures… they probably had a “complex” or transegalitarian social structure. The tool intensification and grave goods point that way.

Thank you! It’s good to see this place reviving. :slight_smile:


#14

Now we have DNA on our side…?

https://www.newscientist.com/article/mg22730324-600-megafauna-extinction-dna-evidence-pins-blame-on-climate-change/


#15

If you read a lot articles and books about prehistory, and you actually pay attention to the time-frame of ice retreat, and the successional changes in types of plant/tree life as temperatures increased, it is obvious that the death of mega-fauna was due to climate and environmental changes. Also, since there was such a tiny population of humans back then, it would be ridiculous to pin the entire blame on them anyway.