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Post by creature386 on Oct 27, 2016 23:38:57 GMT 5
It could be that it took some time for humans to really "diversify" and to really settle until they could become dangerous for the animals. After all, the paper I've cited above claims humans fist appeared in North America 13k years ago (oddly, it claims South America was first inhabited 14.6k years ago, but let's ignore this) which coincides with the time of megafauna extinction. So, is it maybe possible that humans only became "visible" after some time (which would also explain why we initially thought they appeared later than they really did)?
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Post by Infinity Blade on Oct 28, 2016 7:08:11 GMT 5
I guess that's a reasonable suspicion. Maybe studies on what could have potentially "limited" humans (e.g. climate) back then could test your idea.
Is it also possible that humans may have been doing something other than hunting animals to extinction? If I remember correctly, the Aboriginal Australians burned the landscape of Australia, which could have prompted the megafauna of that continent to go extinct. However, I don't know of any evidence for anything similar that Paleo-Indians did.
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Post by Infinity Blade on Dec 29, 2016 10:07:46 GMT 5
I'm not going to be so impulsive or eager to come to a conclusion as Bk Jeong (acepredator) was, but here's a paper he shared on Google Plus. Global late Quaternary megafauna extinctions linked to humans, not climate changeThe late Quaternary megafauna extinction was a severe global-scale event. Two factors, climate change and modern humans, have received broad support as the primary drivers, but their absolute and relative importance remains controversial. To date, focus has been on the extinction chronology of individual or small groups of species, specific geographical regions or macroscale studies at very coarse geographical and taxonomic resolution, limiting the possibility of adequately testing the proposed hypotheses. We present, to our knowledge, the first global analysis of this extinction based on comprehensive country-level data on the geographical distribution of all large mammal species (more than or equal to 10 kg) that have gone globally or continentally extinct between the beginning of the Last Interglacial at 132 000 years BP and the late Holocene 1000 years BP, testing the relative roles played by glacial–interglacial climate change and humans. We show that the severity of extinction is strongly tied to hominin palaeobiogeography, with at most a weak, Eurasia-specific link to climate change. This first species-level macroscale analysis at relatively high geographical resolution provides strong support for modern humans as the primary driver of the worldwide megafauna losses during the late Quaternary.rspb.royalsocietypublishing.org/content/281/1787/20133254 |
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Post by Infinity Blade on Dec 30, 2016 1:05:29 GMT 5
Climate change not to blame for late Quaternary megafauna extinctions in AustraliaLate Quaternary megafauna extinctions impoverished mammalian diversity worldwide. The causes of these extinctions in Australia are most controversial but essential to resolve, because this continent-wide event presaged similar losses that occurred thousands of years later on other continents. Here we apply a rigorous metadata analysis and new ensemble-hindcasting approach to 659 Australian megafauna fossil ages. When coupled with analysis of several high-resolution climate records, we show that megafaunal extinctions were broadly synchronous among genera and independent of climate aridity and variability in Australia over the last 120,000 years. Our results reject climate change as the primary driver of megafauna extinctions in the world’s most controversial context, and instead estimate that the megafauna disappeared Australia-wide ∼13,500 years after human arrival, with shorter periods of coexistence in some regions. This is the first comprehensive approach to incorporate uncertainty in fossil ages, extinction timing and climatology, to quantify mechanisms of prehistorical extinctions.www.nature.com/articles/ncomms10511
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Post by elosha11 on Dec 30, 2016 5:06:37 GMT 5
I always wondered how a human population so much smaller than modern times and armed with only crude weapons and little technology could so drastically reduce comparatively large and stable megafauna populations? But on the other hand, since this was largely pre-agrarian society, it's not like humans could substitute large quantities of vegetables, grains, and domestic animals for food sources. Although I'm sure there was variety in their diet, it wasn't like modern food sources. They probably were constantly targeting large game, which over hundreds/thousands of years may have in turn negatively affected both herbivore and megafauna carnivore populations. And they may have taken more game than they needed, both to insure against starvation and perhaps also from sheer wastefulness/greed. Apparently, our ancestors had destructive tendencies similar to those we exhibit.
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Post by Infinity Blade on May 7, 2017 4:39:27 GMT 5
Megafaunal extinctions driven by too much moistureStudies of bones from Ice Age megafaunal animals across Eurasia and the Americas have revealed that major increases in environmental moisture occurred just before many species suddenly became extinct around 11-15,000 years ago. The persistent moisture resulting from melting permafrost and glaciers caused widespread glacial-age grasslands to be rapidly replaced by peatlands and bogs, fragmenting populations of large herbivore grazers.Research led by the Australian Centre for Ancient DNA (ACAD) at the University of Adelaide, published today in Nature Ecology and Evolution, has revealed that the ancient bones preserve direct biochemical evidence of the environmental upheavals, which can be traced through time. Using 511 radiocarbon dated bones from animals such as bison, horse, and llamas the team was able to investigate the role of environmental change in the mysterious megafaunal extinctions, which claimed the vast majority of existing large land animals such as giant sloths and sabre-toothed cats. "We didn't expect to find such clear signals of moisture increases occurring so widely across all of Europe, Siberia and the Americas," says study leader Professor Alan Cooper, ACAD Director. "The timing varied between regions, but matches the collapse of glaciers and permafrost and occurs just before most species go extinct. The international team of researchers, including the University of Alaska Fairbanks, University of Oslo, the Yukon Government, and palaeontologists across Russia and Canada, measured nitrogen isotopes preserved in dated ancient animal bones and teeth recovered from permafrost areas and caves across Europe, Siberia, North and South America. They found distinctive biochemical signals reflecting massive increases of moisture on the landscape. "Grassland megafauna were critical to the food chains. They acted like giant pumps that shifted nutrients around the landscape," says lead author Dr Tim Rabanus-Wallace, from the University of Adelaide. "When the moisture influx pushed forests and tundras to replace the grasslands, the ecosystem collapsed and took many of the megafauna with it." "The idea of moisture-driven extinctions is really exciting because it can also explain why Africa is so different, with a much lower rate of megafaunal extinctions and many species surviving to this day, says Professor Cooper. "Africa's position across the equator means that grassland zones have always surrounded the central monsoon region. The stable grasslands are what has allowed large herbivores to persist -- rather than any special wariness of hunters learned from humans evolving there." Professor Matthew Wooller, of the University of Alaska Fairbanks, says: "We find that on different continents the climate changes happened at different times, but they all showed that moisture increased massively just prior to extinction. The really elegant feature of this study is that it produces direct evidence from the fossils themselves -- these extinct creatures are informing us about the climate they experienced leading up to their own extinctions." www.sciencedaily.com/releases/2017/04/170418111514.htm
Megafaunal isotopes reveal role of increased moisture on rangeland during late Pleistocene extinctionsM. Timothy Rabanus-Wallace, Matthew J. Wooller, Grant D. Zazula, Elen Shute, A. Hope Jahren, Pavel Kosintsev, James A. Burns, James Breen, Bastien Llamas & Alan Cooper The role of environmental change in the late Pleistocene megafaunal extinctions remains a key question, owing in part to uncertainty about landscape changes at continental scales. We investigated the influence of environmental changes on megaherbivores using bone collagen nitrogen isotopes (n = 684, 63 new) as a proxy for moisture levels in the rangelands that sustained late Pleistocene grazers. An increase in landscape moisture in Europe, Siberia and the Americas during the Last Glacial–Interglacial Transition (LGIT; ~25–10 kyr BP) directly affected megaherbivore ecology on four continents, and was associated with a key period of population decline and extinction. In all regions, the period of greatest moisture coincided with regional deglaciation and preceded the widespread formation of wetland environments. Moisture-driven environmental changes appear to have played an important part in the late Quaternary megafaunal extinctions through alteration of environments such as rangelands, which supported a large biomass of specialist grazers. On a continental scale, LGIT moisture changes manifested differently according to regional climate and geography, and the stable presence of grasslands surrounding the central forested belt of Africa during this period helps to explain why proportionally fewer African megafauna became extinct during the late Pleistocene.www.nature.com/articles/s41559-017-0125
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Post by Infinity Blade on Nov 21, 2017 7:29:58 GMT 5
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Post by Life on Nov 21, 2017 18:42:55 GMT 5
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Post by Infinity Blade on Mar 19, 2019 6:52:42 GMT 5
Climate change not to blame for late Quaternary megafauna extinctions in AustraliaLate Quaternary megafauna extinctions impoverished mammalian diversity worldwide. The causes of these extinctions in Australia are most controversial but essential to resolve, because this continent-wide event presaged similar losses that occurred thousands of years later on other continents. Here we apply a rigorous metadata analysis and new ensemble-hindcasting approach to 659 Australian megafauna fossil ages. When coupled with analysis of several high-resolution climate records, we show that megafaunal extinctions were broadly synchronous among genera and independent of climate aridity and variability in Australia over the last 120,000 years. Our results reject climate change as the primary driver of megafauna extinctions in the world’s most controversial context, and instead estimate that the megafauna disappeared Australia-wide ∼13,500 years after human arrival, with shorter periods of coexistence in some regions. This is the first comprehensive approach to incorporate uncertainty in fossil ages, extinction timing and climatology, to quantify mechanisms of prehistorical extinctions.www.nature.com/articles/ncomms10511 I'm just gonna say it. At least from what I've seen, the megafaunal extinction event in Sahul (Australia+New Guinea+Tasmania as one continent in prehistoric times) was probably anthropogenic in cause. Other continents seem to have experienced some climate changes that could have had a notable impact on the survival of Pleistocene megafauna (see my post with the "too much moisture" study above), but the few most recent studies I'm aware of (albeit dating to 4 or 5 years ago) seem to suggest that humans were the dominant cause; see the third post on this page, as well as Bartlett et al. (2015). |
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Post by Infinity Blade on Mar 30, 2019 2:03:49 GMT 5
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Post by creature386 on Aug 2, 2019 3:18:09 GMT 5
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Post by Infinity Blade on Aug 2, 2019 4:49:55 GMT 5
At first I thought this was an argument against the Blitzkrieg hypothesis, but then I read the second underlined paragraph.
It is an intriguing idea.
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Post by dinosauria101 on Aug 2, 2019 9:26:24 GMT 5
I think I'll put that in the 'Can't believe is legit' thread.
And at the same time, it's somewhat unsurprising. Sounds very human to me
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Post by creature386 on Aug 2, 2019 14:10:51 GMT 5
Yeah, it's not like "destroying the environment to impress your girlfriend" is a thing of the past. I mean, you don't buy an SUV to get from A to B.
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Post by dinosauria101 on Aug 2, 2019 14:16:19 GMT 5
Yeah, it's not like "destroying the environment to impress your girlfriend" is a thing of the past. That's actually a pretty good analogy. It does seem to hod up in this case. |
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