While the Minoan culture on Crete was just beginning, woolly mammoths were disappearing from St. Paul Island, Alaska, according to an international team of scientists who have dated this extinction to 5,600 years ago.
"It's amazing that everything turned out so precisely with dating of extinction at 5,600 plus or minus 100 years," said Russell Graham, professor of geosciences, Penn State."
St. Paul Island lies about 400 miles north of the Aleutian Islands and was part of the Bering Land Bridge before sea level rose when the last glacial period ended. Previous researchers radiocarbon-dated remains of five mammoths to about 6,480 years ago, but there was no way to know if these were the last five animals.
The researchers used a variety of proxies to date the demise of the mammoths on the island. Proxies are things in the environment that can be used to independently document the presence of an organism, even though they are not parts of it. In this study, three different spores from fungi that grow on large animal dung were extracted from lake cores and used to determine when the mammoths were no longer on the island. Proxies in sediments from cores from a lake near the cave were used to determine the time of the demise of the mammoth population.
Giant Ice Age species including elephant-sized sloths and powerful sabre-toothed cats that once roamed the windswept plains of Patagonia, southern South America, were finally felled by a perfect storm of a rapidly warming climate and humans, a new study has shown.
Research led by the Australian Centre for Ancient DNA (ACAD) at the University of Adelaide, published today in Science Advances, has revealed that it was only when the climate warmed, long after humans first arrived in Patagonia, did the megafauna suddenly die off around 12,300 years ago.
The timing and cause of rapid extinctions of the megafauna has remained a mystery for centuries.
"Patagonia turns out to be the Rosetta Stone - it shows that human colonisation didn't immediately result in extinctions, but only as long as it stayed cold," says study leader Professor Alan Cooper, ACAD Director. "Instead, more than 1000 years of human occupation passed before a rapid warming event occurred, and then the megafauna were extinct within a hundred years."
Millennial-scale faunal record reveals differential resilience of European large mammals to human impacts across the Holocene
Authors:
Crees et al
Abstract:
The use of short-term indicators for understanding patterns and processes of biodiversity loss can mask longer-term faunal responses to human pressures. We use an extensive database of approximately 18 700 mammalian zooarchaeological records for the last 11 700 years across Europe to reconstruct spatio-temporal dynamics of Holocene range change for 15 large-bodied mammal species. European mammals experienced protracted, non-congruent range losses, with significant declines starting in some species approximately 3000 years ago and continuing to the present, and with the timing, duration and magnitude of declines varying individually between species. Some European mammals became globally extinct during the Holocene, whereas others experienced limited or no significant range change. These findings demonstrate the relatively early onset of prehistoric human impacts on postglacial biodiversity, and mirror species-specific patterns of mammalian extinction during the Late Pleistocene. Herbivores experienced significantly greater declines than carnivores, revealing an important historical extinction filter that informs our understanding of relative resilience and vulnerability to human pressures for different taxa. We highlight the importance of large-scale, long-term datasets for understanding complex protracted extinction processes, although the dynamic pattern of progressive faunal depletion of European mammal assemblages across the Holocene challenges easy identification of ‘static’ past baselines to inform current-day environmental management and restoration.
The extinction of large animals from tropical forests could make climate change worse -- according to researchers at the University of East Anglia.
New research published today in Science Advances reveals that a decline in fruit-eating animals such as large primates, tapirs and toucans could have a knock-on effect for tree species.
This is because large animals disperse large seeded plant species often associated with large trees and high wood density -- which are more effective at capturing and storing carbon dioxide from the atmosphere than smaller trees.
Seed dispersal by large-bodied vertebrates is via the ingestion of viable seeds that pass through the digestive tract intact.
Removing large animals from the ecosystem upsets the natural balance and leads to a loss of heavy-wooded large trees, which means that less CO2 can be locked away.
The cheetah (Acinonyx jubatus) is now at home on the African plains, but it started a migration 100, 000 years ago from North America towards its current habitat. The research, published in the open access journal Genome Biology, found that the migration from North America was costly for the species, triggering the first major reduction in their gene pool.
The modern African cheetah is found across eastern and southern Africa, but it is highly endangered because of their small free ranging population and inbreeding. Researchers from St. Petersburg State University, Russia, in collaboration with BGI, China and CCF, Namibia, sequenced the genome from a male Namibian cheetah, called 'Chewbaaka', and six other wild cheetahs from Tanzania and Namibia. This gave further insight into the species evolutionary history and the breadth of genome impoverishment, which elevates juvenile mortality, causes extreme abnormalities in sperm development and increases vulnerability to infectious disease outbreaks.
A total of 18 cheetah genes showed damaging mutations and one gene in particular, AKAP4, showed a large number of mutations, which could harm sperm development and may explain why cheetah have a large proportion of defective sperm, and hence their low reproductive success.
The cheetah is descended from a relative of American pumas and their fossil record extends across the Americas, Europe and Asia. The species has suffered two population bottlenecks - an event whereby the population is rapidly reduced due to environmental factors.
The first of these took place 100, 000 years ago, around the late Pleistocene - a geological period shaped by repeated glaciations, when cheetahs started to move towards Asia across the Beringian landbridge and then travelled south to Africa. This migration was punctuated with dwindling populations and limited gene flow due to the individuals' own vast territory boundaries, measuring 300-800 square miles, thereby increasing incestuous mating.
The second bottleneck around 10- 12, 000 years ago, further reduced numbers, leading to further loss of endemic variability observed in modern cheetahs.
A continent-wide assessment of the form and intensity of large mammal herbivory in Africa
Authors:
Hempson et al
Abstract:
Megafaunal extinctions and a lack of suitable remote sensing technology impede our understanding of both the ecological legacy and current impacts of large mammal herbivores in the Earth system. To address this, we reconstructed the form and intensity of herbivory pressure across sub-Saharan Africa ~1000 years ago. Specifically, we modeled and mapped species-level biomass for 92 large mammal herbivores using census data, species distributions, and environmental covariates. Trait-based classifications of these species into herbivore functional types, and analyses of their biomass surfaces, reveal four ecologically distinct continental-scale herbivory regimes, characterized by internally similar forms and intensities of herbivory pressure. Associations between herbivory regimes, fire prevalence, soil nutrient status, and rainfall provide important insights into African ecology and pave the way for integrating herbivores into global-scale studies.
The larger mammal fauna from the Lower Paleolithic Schöningen Spear site and its contribution to hominin subsistence
Authors:
van Kolfschoten et al
Abstract:
The locality Schöningen (Germany) is an important source of knowledge about Lower Paleolithic hominin subsistence. The locality includes a series of sites dated to the late Middle Pleistocene with a Holsteinian (MIS 11) and Reinsdorf Interglacial (MIS 9) age. One of the youngest sites is Schöningen 13 II-4, the Spear Horizon site also known as the Horse Butchery site. The organic remains excavated here are exceptionally well-preserved as they were embedded in anaerobic, waterlogged sediments in an area where the groundwater is rich in calcium carbonate. The fossil assemblage is ideal for the study of patterns in hominin interference with the mammalian species encountered at the site.
The vertebrate record is extensive and very diverse. The fossil larger carnivore guild of the Spear Horizon faunal assemblage includes saber-toothed cat, fox, and wolf. Herbivores are represented by an elephant species, two equid species, two rhinoceros species, two cervid species, and two large bovid species.
Evidence of hominin interference presents itself as either marks on skeletal remains related to the use of bones as knapping tools or hammers, or as marks that indicate butchering activities such as skinning, dismembering, defleshing, filleting, and marrow extraction. The humerus of the saber-toothed cat clearly shows that the bone has been used as a knapping tool. The fossil remains of the other larger carnivores do not show any signs of hominin interference or exploitation. This also applies to the limited number of elephant and rhinoceros remains found at the site. The large horse Equus mosbachensis dominates the larger mammal record and played a major role in hominin subsistence. Marks on the horse bones indicate that a large number of carcasses have been butchered. Traces on the fossil remains of both red deer (Cervus elaphus) and the large bovids also indicate exploitation by Lower Paleolithic hominins.
If Pleistocene megafauna -- mastodons, mammoths, giant sloths and others -- had not become extinct, humans might not be eating pumpkin pie and squash for the holidays, according to an international team of anthropologists.
"It's been suggested before and I think it's a very reasonable hypothesis, that wild species of pumpkin and squash weren't used for food early in the domestication process," said Logan Kistler, NERC Independent Research Fellow, University of Warwick, U.K. and recent Penn State postdoctoral fellow. "Rather, they might have been useful for a variety of other purposes like the bottle gourd, as containers, tools, fishnet floats, etc. At some point, as a symbiotic relationship developed, palatability evolved, but the details of that process aren't known at the present."
Researchers believe that initially humans did not eat wild pumpkin and squash -- members of the cucurbita family -- because the wild fruit is not only bitter but also toxic to humans and smaller animals. However, clear evidence exists that very large animals -- megafauna -- that lived 12,000 years ago did eat these fruit.
"Lee Newsom (associate professor of anthropology, Penn State and study co-author) has recovered many wild gourd/squash seeds from ancient Mastodon dung, suggesting that large herbivores may have been an important feature in the natural history of these wild plants," said Kistler.
The researchers looked at varieties of modern domestic cucurbits, modern wild cucurbits and archaeological specimens. They believe that changes in distribution of the wild plants are directly related to the disappearance of the large animals.
Archaeologists with The Australian National University (ANU) have discovered fossils of seven giant rat species on East Timor, with the largest up to 10 times the size of modern rats.
Dr Julien Louys of the ANU School of Culture, History and Language, who is helping lead the project said these are the largest known rats to have ever existed.
"They are what you would call mega-fauna. The biggest one is about five kilos, the size of a small dog," Dr Louys said.
"Just to put that in perspective, a large modern rat would be about half a kilo."
The work is part of the From Sunda to Sahul project which is looking at the earliest human movement through Southeast Asia. Researchers are now trying to work out exactly what caused the rats to die out.
Dr Louys said the earliest records of humans on East Timor date to around 46,000 years ago, and they lived with the rats for thousands of years.
"We know they're eating the giant rats because we have found bones with cut and burn marks," he said.
"The funny thing is that they are co-existing up until about a thousand years ago. The reason we think they became extinct is because that was when metal tools started to be introduced in Timor, people could start to clear forests at a much larger scale."
Life and extinction of megafauna in the ice-age Arctic
Authors:
Mann et al
Abstract:
Understanding the population dynamics of megafauna that inhabited the mammoth steppe provides insights into the causes of extinctions during both the terminal Pleistocene and today. Our study area is Alaska's North Slope, a place where humans were rare when these extinctions occurred. After developing a statistical approach to remove the age artifacts caused by radiocarbon calibration from a large series of dated megafaunal bones, we compare the temporal patterns of bone abundance with climate records. Megafaunal abundance tracked ice age climate, peaking during transitions from cold to warm periods. These results suggest that a defining characteristic of the mammoth steppe was its temporal instability and imply that regional extinctions followed by population reestablishment from distant refugia were characteristic features of ice-age biogeography at high latitudes. It follows that long-distance dispersal was crucial for the long-term persistence of megafaunal species living in the Arctic. Such dispersal was only possible when their rapidly shifting range lands were geographically interconnected. The end of the last ice age was fatally unique because the geographic ranges of arctic megafauna became permanently fragmented after stable, interglacial climate engendered the spread of peatlands at the same time that rising sea level severed former dispersal routes.
Variable impact of late-Quaternary megafaunal extinction in causing ecological state shifts in North and South America
Authors:
Barnosky et al
Abstract:
Loss of megafauna, an aspect of defaunation, can precipitate many ecological changes over short time scales. We examine whether megafauna loss can also explain features of lasting ecological state shifts that occurred as the Pleistocene gave way to the Holocene. We compare ecological impacts of late-Quaternary megafauna extinction in five American regions: southwestern Patagonia, the Pampas, northeastern United States, northwestern United States, and Beringia. We find that major ecological state shifts were consistent with expectations of defaunation in North American sites but not in South American ones. The differential responses highlight two factors necessary for defaunation to trigger lasting ecological state shifts discernable in the fossil record: (i) lost megafauna need to have been effective ecosystem engineers, like proboscideans; and (ii) historical contingencies must have provided the ecosystem with plant species likely to respond to megafaunal loss. These findings help in identifying modern ecosystems that are most at risk for disappearing should current pressures on the ecosystems’ large animals continue and highlight the critical role of both individual species ecologies and ecosystem context in predicting the lasting impacts of defaunation currently underway.
Combining paleo-data and modern exclosure experiments to assess the impact of megafauna extinctions on woody vegetation
Authors:
Bakker et al
Abstract:
Until recently in Earth history, very large herbivores (mammoths, ground sloths, diprotodons, and many others) occurred in most of the World’s terrestrial ecosystems, but the majority have gone extinct as part of the late-Quaternary extinctions. How has this large-scale removal of large herbivores affected landscape structure and ecosystem functioning? In this review, we combine paleo-data with information from modern exclosure experiments to assess the impact of large herbivores (and their disappearance) on woody species, landscape structure, and ecosystem functions. In modern landscapes characterized by intense herbivory, woody plants can persist by defending themselves or by association with defended species, can persist by growing in places that are physically inaccessible to herbivores, or can persist where high predator activity limits foraging by herbivores. At the landscape scale, different herbivore densities and assemblages may result in dynamic gradients in woody cover. The late-Quaternary extinctions were natural experiments in large-herbivore removal; the paleoecological record shows evidence of widespread changes in community composition and ecosystem structure and function, consistent with modern exclosure experiments. We propose a conceptual framework that describes the impact of large herbivores on woody plant abundance mediated by herbivore diversity and density, predicting that herbivore suppression of woody plants is strongest where herbivore diversity is high. We conclude that the decline of large herbivores induces major alterations in landscape structure and ecosystem functions.
pop sci write up.
2nd one.
Global nutrient transport in a world of giants
Authors:
Doughty et al
Abstract:
The past was a world of giants, with abundant whales in the sea and large animals roaming the land. However, that world came to an end following massive late-Quaternary megafauna extinctions on land and widespread population reductions in great whale populations over the past few centuries. These losses are likely to have had important consequences for broad-scale nutrient cycling, because recent literature suggests that large animals disproportionately drive nutrient movement. We estimate that the capacity of animals to move nutrients away from concentration patches has decreased to about 8% of the preextinction value on land and about 5% of historic values in oceans. For phosphorus (P), a key nutrient, upward movement in the ocean by marine mammals is about 23% of its former capacity (previously about 340 million kg of P per year). Movements by seabirds and anadromous fish provide important transfer of nutrients from the sea to land, totalling ∼150 million kg of P per year globally in the past, a transfer that has declined to less than 4% of this value as a result of the decimation of seabird colonies and anadromous fish populations. We propose that in the past, marine mammals, seabirds, anadromous fish, and terrestrial animals likely formed an interlinked system recycling nutrients from the ocean depths to the continental interiors, with marine mammals moving nutrients from the deep sea to surface waters, seabirds and anadromous fish moving nutrients from the ocean to land, and large animals moving nutrients away from hotspots into the continental interior.
pop sci write up.
The impact of large terrestrial carnivores on Pleistocene ecosystems
Authors:
Van Valkenburgh et al
Abstract:
Large mammalian terrestrial herbivores, such as elephants, have dramatic effects on the ecosystems they inhabit and at high population densities their environmental impacts can be devastating. Pleistocene terrestrial ecosystems included a much greater diversity of megaherbivores (e.g., mammoths, mastodons, giant ground sloths) and thus a greater potential for widespread habitat degradation if population sizes were not limited. Nevertheless, based on modern observations, it is generally believed that populations of megaherbivores (>800 kg) are largely immune to the effects of predation and this perception has been extended into the Pleistocene. However, as shown here, the species richness of big carnivores was greater in the Pleistocene and many of them were significantly larger than their modern counterparts. Fossil evidence suggests that interspecific competition among carnivores was relatively intense and reveals that some individuals specialized in consuming megaherbivores. To estimate the potential impact of Pleistocene large carnivores, we use both historic and modern data on predator–prey body mass relationships to predict size ranges of their typical and maximum prey when hunting as individuals and in groups. These prey size ranges are then compared with estimates of juvenile and subadult proboscidean body sizes derived from extant elephant growth data. Young proboscideans at their most vulnerable age fall within the predicted prey size ranges of many of the Pleistocene carnivores. Predation on juveniles can have a greater impact on megaherbivores because of their long interbirth intervals, and consequently, we argue that Pleistocene carnivores had the capacity to, and likely did, limit megaherbivore population sizes.
Exploring the influence of ancient and historic megaherbivore extirpations on the global methane budget
Authors:
Smith et al
Abstract:
Globally, large-bodied wild mammals are in peril. Because “megamammals” have a disproportionate influence on vegetation, trophic interactions, and ecosystem function, declining populations are of considerable conservation concern. However, this is not new; trophic downgrading occurred in the past, including the African rinderpest epizootic of the 1890s, the massive Great Plains bison kill-off in the 1860s, and the terminal Pleistocene extinction of megafauna. Examining the consequences of these earlier events yields insights into contemporary ecosystem function. Here, we focus on changes in methane emissions, produced as a byproduct of enteric fermentation by herbivores. Although methane is ∼200 times less abundant than carbon dioxide in the atmosphere, the greater efficiency of methane in trapping radiation leads to a significant role in radiative forcing of climate. Using global datasets of late Quaternary mammals, domestic livestock, and human population from the United Nations as well as literature sources, we develop a series of allometric regressions relating mammal body mass to population density and CH4 production, which allows estimation of methane production by wild and domestic herbivores for each historic or ancient time period. We find the extirpation of megaherbivores reduced global enteric emissions between 2.2–69.6 Tg CH4 y−1 during the various time periods, representing a decrease of 0.8–34.8% of the overall inputs to tropospheric input. Our analyses suggest that large-bodied mammals have a greater influence on methane emissions than previously appreciated and, further, that changes in the source pool from herbivores can influence global biogeochemical cycles and, potentially, climate.
Sea otters, kelp forests, and the extinction of Steller’s sea cow
Authors:
Estes et al
Abstract:
The late Pleistocene extinction of so many large-bodied vertebrates has been variously attributed to two general causes: rapid climate change and the effects of humans as they spread from the Old World to previously uninhabited continents and islands. Many large-bodied vertebrates, especially large apex predators, maintain their associated ecosystems through top-down forcing processes, especially trophic cascades, and megaherbivores also exert an array of strong indirect effects on their communities. Thus, a third possibility for at least some of the Pleistocene extinctions is that they occurred through habitat changes resulting from the loss of these other keystone species. Here we explore the plausibility of this mechanism, using information on sea otters, kelp forests, and the recent extinction of Steller's sea cows from the Commander Islands. Large numbers of sea cows occurred in the Commander Islands at the time of their discovery by Europeans in 1741. Although extinction of these last remaining sea cows during early years of the Pacific maritime fur trade is widely thought to be a consequence of direct human overkill, we show that it is also a probable consequence of the loss of sea otters and the co-occurring loss of kelp, even if not a single sea cow had been killed directly by humans. This example supports the hypothesis that the directly caused extinctions of a few large vertebrates in the late Pleistocene may have resulted in the coextinction of numerous other species.
Radiocarbon analysis of the decline and extinction of large mammals in the Americas lends support to the idea that hunting by humans led to the animals' demise -- and backs the generally accepted understanding of when humans arrived in, and how they colonized, the Western Hemisphere.
Those findings by University of Wyoming researchers are reported this week in an article published in the Proceedings of the National Academy of Sciences, a major scientific journal. The study was conducted by Professor Todd Surovell and graduate student Spencer Pelton in UW's Department of Anthropology; Professor Richard Anderson-Sprecher in the Department of Statistics; and Assistant Professor Adam Myers in the Department of Physics and Astronomy.
Their work supports a hypothesis forwarded in 1973 by well-known geoscientist Paul Martin that the chronology of the extinction of animals such as mammoths, mastodons, camels, horses and ground sloths in the Americas could be used to map the spread of humans through the New World.
"The heavy ecological footprint of human societies throughout prehistory is becoming increasingly apparent through a variety of environmental (indicators) independent of the archeological record," the researchers wrote. "Past human societies have disrupted ecological communities in dramatic ways for many tens, if not hundreds of thousands, of years."
The study involved compiling radiocarbon dates from fossils of now-extinct animals from North and South America, and looking at how those dates correspond with initial evidence of human colonization. The researchers found that, as Martin predicted, decline and extinction of the large mammals began between 13,300-15,000 years ago in Alaska and areas near the Bering Strait; between 12,900-13,200 years ago in the contiguous United States; and between 12,600-13,900 years ago in South America.
That supports the generally accepted understanding of how humans colonized the Americas: first, that they crossed from Siberia to Alaska across a Bering Strait land bridge; and then that they moved southward across North America and into South America. Hunting of the native large mammals is thought to have fueled rapid human population growth and expansion.
A number of hypotheses have been forwarded to explain the extinction of those animals. The "overkill hypothesis" connects their demise directly to overhunting by humans, and that is supported by the north-to-south extinction trend observed in the new study.
Pleistocene megafaunal interaction networks became more vulnerable after human arrival
Authors:
Pires et al
Abstract:
The end of the Pleistocene was marked by the extinction of almost all large land mammals worldwide except in Africa. Although the debate on Pleistocene extinctions has focused on the roles of climate change and humans, the impact of perturbations depends on properties of ecological communities, such as species composition and the organization of ecological interactions. Here, we combined palaeoecological and ecological data, food-web models and community stability analysis to investigate if differences between Pleistocene and modern mammalian assemblages help us understand why the megafauna died out in the Americas while persisting in Africa. We show Pleistocene and modern assemblages share similar network topology, but differences in richness and body size distributions made Pleistocene communities significantly more vulnerable to the effects of human arrival. The structural changes promoted by humans in Pleistocene networks would have increased the likelihood of unstable dynamics, which may favour extinction cascades in communities facing extrinsic perturbations. Our findings suggest that the basic aspects of the organization of ecological communities may have played an important role in major extinction events in the past. Knowledge of community-level properties and their consequences to dynamics may be critical to understand past and future extinctions.
Megafauna Extinction in South America: A new chronology for the Argentine Pampas
Authors:
Prado et al
Abstract:
The megafauna extinction in South America was one of the most profound events, with the loss of 50 genera (~ 83%). Three orders disappeared (Notoungulata, Proboscidea, Litopterna), as did all large xenarthrans, but how this fits into global extinction is uncertain, mainly due to the lack of chronological resolution. In recent years there has been an increase in the number of radiocarbon dating at archaeological and paleontological sites, but this information varies greatly from area to area in South America, and few data can be considered to constitute a taxon-date.
The timing of the late Pleistocene extinction in the Pampas is poorly established. Most taxa only appear in the biostratigraphic context and many reported 14C dates do not meet rigorous criteria for accepting dates, including reports suggesting survival of megafauna into the Holocene. In the present paper, we evaluate the published radiocarbon dates in the pampas and present 20 new radiocarbon dates for paleontological sites in order to establish a more accurate “extinction window” for the key taxa. These new dates are sufficiently robust to assess correspondences among last-appearance records of megafauna, first-appearance records of humans, and the Younger Dryas to Holocene climatic transition in the Argentine Pampas. These results highlight the need for greater effort in taxa selection for dating.
