Tag: climate change

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Climate change greatly impacted extinction of Neanderthals

What are stalagmites? Stalagmites grow in thin layers each year and any change in temperature alters their chemical composition. The layers therefore preserve a natural archive of climate change over many thousands of years. The researchers examined stalagmites in two Romanian caves, which revealed more detailed records of climate change in continental Europe than had previously been available. From looking closely at the layers of the stalagmites, the archaeologists were able to identify a series of prolonged cold and dry periods in Europe between 44,000 and 40,000 years ago. Temperatures would gradually cool, staying very cold for centuries or even millennia, and then warm up again very abruptly.

Neanderthal presence declined during cold periods

These cold periods coincide with the timings of a near complete absence of archaeological artefacts from the Neanderthals. From this, it has been suggested that changes in climate had a significant impact on the long-term survival of Neanderthal man. [caption id="attachment_8774" align="aligncenter" width="500"] A model an adult Neanderthal male head and shoulders on display in the Hall of Human Origins in the Smithsonian Museum of Natural History in Washington, D.C. Credit: Tim Evanson[/caption] Dr Vasile Ersek is co-author of the study and a senior lecturer in physical geography in Northumbria University’s Department of Geography and Environmental Sciences. He explains: “The Neanderthals were the human species closest to ours and lived in Eurasia for some 350,000 years. However, around 40,000 years ago – during the last Ice Age and shortly after the arrival of anatomically modern humans in Europe – they became extinct. “For many years we have wondered what could have caused their demise. Were they pushed ‘over the edge’ by the arrival of modern humans, or were other factors involved? Our study suggests that climate change may have had an important role in the Neanderthal extinction.”

Why did modern humans survive cold periods?

The researchers have stated that modern humans survived these cold conditions – known as stadial periods – because they were more adaptable to their environment. [caption id="attachment_8773" align="aligncenter" width="500"] Credit: Le Moustier Neanderthals by Charles R Knight, 1920[/caption] While Neanderthals were skilled hunters and were able to use fire, their diet wasn’t as diverse as that of modern humans. They lived mainly on meat, so when that food source became more scarce during colder periods, Neanderthals became vulnerable. By this time, modern humans had begun to incorporate fish and plants into their diet – potentially marking them for survival.

Depopulation, repopulation

According to Dr Ersek, the research team’s findings have indicated that this cycle of “hostile climate intervals” over thousands of years, in which the climate varied abruptly and was characterised by extreme cold temperatures, was responsible for the future European demographic. “Before now, we did not have climate records from the region where Neanderthals lived which had the necessary age accuracy and resolution to establish a link between when Neanderthals died out and the timing of these extreme cold periods,” he said, “But our findings indicate that the Neanderthal populations successively decreased during the repeated cold stadials. “When temperatures warmed again, their smaller populations could not expand as their habitat was also being occupied by modern humans and this facilitated a staggered expansion of modern humans into Europe. “The comparable timing of stadials and population changes seen in the archaeologic and genetic record suggests that millennial-scale hostile climate intervals may have been the pacesetter of multiple depopulation-repopulation cycles. These cycles ultimately drew the demographic map of Europe’s Middle-Upper Paleolithic transition.” Read more about the difference between Neanderthals and modern humans here.]]>

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Ancient dirty dishes shed light on early climate change – and how farmers adapted

A major climate event Looking closely at the Neolithic and Chalcolithic city settlement of Çatalhöyük in southern Anatolia, Turkey, the study takes into account farming practices in the period spanning 7500 BC to 5700 BC. When the city was most intensely occupied around 8,200 years ago, there was a sudden decrease in global temperatures. It became a well-documented event in the history of climate change, and was caused by a huge amount of glacial meltwater from a massive freshwater lake in northern Canada.   [caption id="attachment_8875" align="aligncenter" width="800"] An artist’s reconstruction of the east and west mounds at Çatalhöyük. Image Credit: Çatalhöyük Research Project[/caption]

Pragmatic farming during drought

The research centres on animal bones found at the excavation site. Scientists have concluded that the herders of the city turned towards sheep and goats, as they fared better during times of drought than cattle. By looking at the cut marks on the animal bones, we can also find more information on butchery practices. They indicate desperation in the community: the high number of cut marks on the bones during the time of the temperature drop shows how the populace exploited any meat available as food would have been scarce.

Dirty dishes

Ancient cooking pots with traces of animal fats have also been analysed in the study, which makes this the first time compounds from animal fats found in pottery are shown to carry evidence for the climate event. [caption id="attachment_8874" align="aligncenter" width="500"] In situ pottery at the archaeological site of Çatalhöyük. The pottery has been at the centre of recent research shedding light on the ways ancient farming practices adapted to climate change. Image credit: Çatalhöyük Research Project.[/caption]

Inevitable impacts

The paper brings together researchers from the University of Bristol’s Organic Geochemistry Unit (School of Chemistry) and the Bristol Research Initiative for the Dynamic Global Environment (School of Geographical Sciences). Co-authors of the paper include archaeologists and archaeozoologists involved in the excavations and the study of the pottery and animal bones from the site. Dr Mélanie Roffet-Salque lead the research. She says: “Changes in precipitation patterns in the past are traditionally obtained using ocean or lake sediment cores. “This is the first time that such information is derived from cooking pots. We have used the signal carried by the hydrogen atoms from the animal fats trapped in the pottery vessels after cooking. “This opens up a completely new avenue of investigation – the reconstruction of past climate at the very location where people lived using pottery.” Co-author, Professor Richard Evershed, adds: “It is really significant that the climate models of the event are in complete agreement with the H signals we see in the animal fats preserved in the pots. “The models point to seasonal changes farmers would have had to adapt to – overall colder temperatures and drier summers – which would have had inevitable impacts on agriculture.”]]>

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How barley spread across the world & helped culture formation

Different routes – an indicator of different cultures? Due to the fact that there were a number of different eastward routes for the spread of the barley population, the study suggests humans were choosing routes based on particular attributes of acting according to environmental adaptation. Choice and environment, therefore, are crucial factors for the spread of staple foods in prehistory. These different routes include ones to the north and south of the Iranian Plateau; through the Inner Asian Mountain Corridor in Central Asia, possibly connecting up to the Chinese section of the Silk Road; a high altitude spread on the southern edge of the Tibetan Plateau; a high latitude spread through the northern steppe; two distinct spreads into Japan; and a maritime route from South Asia. As previous research has provided radiocarbon dates, we know when the routes were followed. [caption id="attachment_8836" align="aligncenter" width="728"] Map showing proposed routes of spread of six different ancestral populations of barley landraces. Direct radiocarbon dates from archaeological barley grain have enabled the timing of these different routes to be elucidated. Credit: D. Lister[/caption]

Impacting rice-growing in East Asia

Lead author Dr Diane Lister, a researcher at the McDonald Institute for Archological Research at the University of Cambridge, says: “One barley population is widespread, particularly around the coastlines. This population may have travelled eastwards via a maritime route from South Asia, via Southeast Asia. This particular population is made up of winter-sown varieties of barley, which are thought to be important in rice-growing areas of East Asia, where a crop of rice is commonly grown in the summer months, and barley adapted to winter-sowing regimes can be planted after the rice harvest. The development of multi-cropping practices during prehistory is thought to have greatly increased productivity and stability, enabling more complex societies to develop.” [caption id="attachment_8837" align="aligncenter" width="257"] Diane Lister at work in the Glyn Daniel laboratory for archaeogenetics at the McDonald Institute for Archaeological Research, University of Cambridge Credit: A. Clarke[/caption]

Moulding Tibetan culture

“Another barley population predominates on the high Tibetan Plateau. This barley has a naked grain, making it a particularly attractive staple, as it doesn’t require the pearling process that hulled barley requires for human consumption. Along with the herding of yak, this naked type of barley is an essential for the Tibetan way of life, and their importance are clearly seen in the offerings of naked barley grains and yak butter in Tibetan Buddhist temples around the region. The staple carbohydrate eaten by the Tibetans is tsampa, made from roasted naked barley flour and mixed with salty Tibetan butter tea.” [caption id="attachment_8835" align="aligncenter" width="590"] Ethnically Tibetan women winnowing naked barley on a road on the edge of the Tibetan Plateau, near Xiahe, Gansu Province, China.
Photo credits Diane Lister[/caption]

New findings contribute to conversation around climate change

So what does this mean for today? Lister concludes: “Barley is an extremely hardy crop, able to grow in regions where other crops are unable to grow, and is an important staple in such environments. Understanding the spread of its cultivation during prehistory, and the various factors that affected its establishment in different regions of Eurasia, will contribute towards our understanding of climate change and its current and future effects on agriculture.” The paper has been published as a part of the Food Globalization in Prehistory project, funded by the European Research Council and awarded to Prof. Martin Jones. Additional funding was provided by a Royal Society International Joint Project grant.]]>

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How intense Ice Age fishing led to the invention of pottery as we know it

Jōmon pottery from the Kanagawa Prefecture, Japan. Credit: Nara National Research Institute for Cultural Properties.[/caption] Examined over a course of three years by researchers from Japan, the Netherlands, Sweden and the University of York’s BioArCh, the findings indicate that ceramics were used by our gatherer-hunter ancestors to initially store and process fish. As fishing techniques evolved and intensified, the range extended to include shellfish, freshwater and marine fish and even mammals. Until recently, ceramic vessels were associated with the arrival of farming. This study, however, debunks that theory. We now know that pottery was a much earlier gatherer-hunter innovation, and was used for the consumption of fish. Professor Oliver Craig, from the Department of Archaeology and Director of the BioArCh research centre at York, who led the study, said: “Our results demonstrate that pottery had a strong association with the processing of fish, irrespective of the ecological setting.” Some of the pottery dates from the end of the Late Pleistocene period: a time when our ancestors were navigating glacial conditions. Other ceramics included in the study are from the post-glacial period, when the climate reached a level close to our current temperature, allowing pottery to be produced in a much greater quantity. Craig continues: “Contrary to expectations, this association remained stable even after the onset of warming, including in more southerly areas, where expanding forests provided new opportunities for hunting and gathering. “The results indicate that a broad array of fish was processed in the pottery after the end of the last Ice Age, corresponding to a period when hunter-gatherers began to settle in one place for longer periods and develop more intensive fishing strategies. [caption id="attachment_8832" align="aligncenter" width="634"] A reconstructed early pottery vessel from Torihama, Japan, dating to the end of the Late Pleistocene (ca 12,000 years old). Chemical analysis revealed that such vessels were used to process fish during the late Glacial period. Credit: Wakasa History and Folklore Museum, Fukui, Japan[/caption] “We suggest this marks a significant change in the role of pottery of hunter-gatherers, corresponding massively increased volume of production, greater variation in forms and sizes and the onset of shellfish exploitation.” Researchers used advanced technologies to recover diagnostic lipids from the charred surface deposits of the vessels. Most of the compounds derive from the processing of freshwater or marine organisms. Because of findings like this, we now know that ceramics played a key role in the ways pre-historic gatherer-hunters consumed fish. Lead author, Dr Alex Lucquin, from BioArCh, Department of Archaeology, University of York, said: “Thanks to the exceptional preservation of traces of animal fat, we now know that pottery changed from a rare and special object to an every-day tool for preparing fish. “I think that our study not only reveals the subsistence of the ancient Jomon people of Japan but also its resilience to a dramatic change in climate.” Dr Simon Kaner, from the University of East Anglia, who was also involved in the study, added: “The research highlights the benefits of this kind of international collaboration for unlocking some of the big questions about the human past, and the potential of engaging with established research networks as created by the Sainsbury Institute over the years.”]]>

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Maya and Ancestral Puebloans Providing Clues on World Water Crisis

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Case For the Anthropocene? Megafauna, Ice Ages and Man-Made Deserts

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The death of megafauna Some scholars have suggested that humans started making irreversible changes to the planet as far back as ten thousand years ago. When humanity first started to spread across the globe spectacular megafauna inhabited the continents, from Wooly Mammoths in the Northern Hemisphere to giant kangaroos in Australia. Many of these creatures are now extinct, with scientists debating intensely whether this was the result of human activity – such as hunting or competition for food, the drastic climate change at the end of the Ice Age; or a mixture of both. If these mass extinctions were driven by humans, it would signify a massive, permanent change to the planet’s ecosystems. Ecosystem Makers Humanity’s influence has not necessarily been just destructive. There is an increasing number of scientists and archaeologists who argue that two of the planet’s most awe-inspiring ecosystems: the Amazon rainforest and the Sahara Desert, could have been created by human activity. Fertile land found radiating from the remains of ancient settlements in recent years has led some archaeologists to claim that for millennia a massive civilisation once inhabited the Amazon, enriching the soil to allow the rainforest to grow. Earlier this year, a new study looked at the distribution of various tree species to add further support to the idea the Amazon was shaped by human hand thousands of years ago. Earlier this year, a research study claimed humans may have played a role in turning the Sahara from green, fertile and dotted with lakes 10,000 years ago to the desert it is today. The research suggests that the arrival of pastoralism to the Sahara could have upset the region’s ecosystem, cleared vegetation leading to an increased albedo and drastic reduction in rainfall. The theory is a relatively new one, but the team behind it are continuing their search for more evidence to support it. The Little Ice Age A 1677 painting by Abraham Hondius depicts ice skaters on London’s River Thames. To any modern Londoner, such a sight seems unthinkable. The seventeenth century was characterised by plummeting temperatures on a global scale however, which some historians label the Little Ice Age. A number of explanations have been offered for this prolonged period of unusually low temperatures, from increased volcanic activity blocking the sun’s radiation to changing ocean current flows. Some have even suggested a shift in the earth’s orbital cycle could have caused the freeze. Another argument posits a human explanation. Specifically, some scientists claim that the massive population loss in the Americas following the arrival of Europeans led to a huge decline in agriculture and process of reforestation substantial enough to change the oxygen/carbon ratio in the atmosphere and generate a cooling effect. Killing the Aral Sea As recently as the 1970s the Aral Sea was the fourth largest lake in the world, yet only 10% of it now remains, leaving a desert in its place. Situated between Kazakhstan and Uzbekistan, the Aral Sea’s disappearance took less than forty years. In the 1960s irrigation projects by the Soviet Union saw the two main rivers feeding the lake diverted. The consequences have been terrifying. The climate in the area has changed massively due to a huge reduction in rainfall. Fishing communities have been devastated by lost livelihoods. Toxic gases rise from the exposed seabeds, leading to dangerous levels of pollution in the area. Ecosystems that once flourished in the Aral Sea are now all but extinct. Meanwhile, dust storms caused by the dried up land have caused nearby glaciers to melt much faster, in turn leading to massive reductions in the amount of drinking water. Radiation The 1950 date chosen by the Working Group on the Anthropocene is heavily tied in with the proliferation of nuclear weapons and power. Although atomic bombs were being tested in the USA in the 1940s, with the first two used in anger against Japan in 1945, it was in the 1950s that nuclear weapons went global. The nuclear arms race saw more and more countries testing weapons of mass destruction, while nuclear power stations also sprung up around the globe to meet a growing energy demand. These saw radioactive elements flung across the planet, having an immeasurable impact on the environment. There are of course countless other examples which could be mentioned, all of which point to the impact mankind has had on the planet. Some are debatable, some speculative, others, such as the drying of the Aral Sea, impossible to deny. Whether one believes we live in the Anthropocene or not, mankind has undoubtedly left a dramatic mark on the delicate ecosystems and environment of the planet. ]]>

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Humans May Have Turned The Sahara to Desert

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Frontiers in Earth Science, can be found online at here]]>

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Early Chinese Culture Altered by Shifting Monsoons

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Proceedings of the National Academy of Sciences, can be found here Image courtesy of Yonaton Goldsmith ]]>

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Catastrophic Climate Change Caused Native Americans' Decline

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Scientific Reports believe the finger can be pointed at climate change. The researchers from the Indiana University-Purdue University Indianapolis used proxies of prehistoric temperature and precipitation preserved in finely layered lake sediments to track the dramatic environmental changes faced by the Mississippians. The lake sediments can be used to map changing climatic conditions in much the same way as tree rings can to detect historical periods of drought. Links appeared between environmental changes, and periods of flourishing or disaster for the Midwestern Native American population. The authors of the study theorise that the extreme climate change they observed likely devastated Mississippian food production, triggering the civilisation’s dramatic disappearance. “Abrupt climate change can impose conditions like drought. If these conditions are severe and sustained, as we have determined that they became for the Mississippians, it is virtually impossible for societies, especially those based on agriculture, to survive,” said corresponding author of the new study, paleoclimatologist Broxton Bird. “From the lake records, we saw that the abundant rainfall and consistent good weather — which supported Mississippian society as it grew — changed, making agriculture unsustainable.” It seems likely that the failure of the Mississippians’ main source of food would have triggered political and social instability, in turn stretching the bonds which held communities together. “Archeologists have recognized that from 1300 onward, Mississippian villages started disappearing –one after the other — almost like lightbulbs in a string, but the question has always been ‘why?,'” said archaeologist Jeremy Wilson, a co-author of the study. “Dr. Bird and his students have shown from the lake-sediment evidence that during the period known as the Little Ice Age, from 1300 to 1800, there was a profound change in climate to colder and drier conditions, which would have negatively impacted the growing of maize in and around Mississippian villages.” The decline of the Mississippians coincided with lower temperatures and reduced rainfall, a consequence of El Nino like conditions in the Pacific Ocean and an overall period of cooling during the little Ice Age. These complicated weather patterns would have ultimately caused drought like conditions in the Midwest. “Climate change had been previously postulated as one of the factors responsible for the disappearance of the Mississippians,” Bird said. “What our research did was develop the highest-resolution record yet produced of rainfall in the midcontinental U.S. for the last 2,100 years, including the time frame from the beginning of the Mississippian period — about 1,000 years ago — to 500 years ago, when much of the lower Midwest was totally abandoned by these people. Our results strongly support climate change — drought, specifically — as a significant cause of the disappearance of Mississippians from the midcontinent through its impact on their ability to farm and produce food surpluses.” Bird suggests that the fate of the Mississippians could provide a valuable lesson for those living and working in the Midwest now. “Mississippians did not have irrigation and relied on rainfall to grow their crops. Modern agriculture in the Midwest corn belt likewise relies on rainfall with very little irrigation infrastructure, making us similarly vulnerable to drought,” The authors of the study are continuing their research at additional lakes in the US Midwest, particularly those close to archaeological sites, in the hope of gaining further insight into the fate of Native American populations. ]]>

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Faeces Eating Fungus Shows Humans Sent Megafauna Extinct

australian-megafauna

Nature Communications places the blame firmly on humans. Typically, explanations for the extinction of Australian megafauna have focused on either climate change or hunting by humans. The new study, led by scientists from Monash University in Victoria, Australia and the University of Colorado Boulder, has used the ancient faeces left behind by the megafauna to reach its conclusion. The team used a sediment core drilled from the Indian Ocean off the southwest coast of Australia to reconstruct past climate and ecosystems on the continent. The sediment core contains chronological layers of material blown into the ocean including ash, dust, pollen and spores from a fungus known as Sporormiella which thrived on the dung of plant eating mammals. Analysis of the sediment revealed that spores from Sporormiella were in abundance from 150,000 years ago, until plummeting around 45,000 years ago. “The abundance of these spores is good evidence for a lot of large mammals on the southwestern Australian landscape up until about 45,000 years ago,” said Professor Gifford Miller from CU Bolder’s Department of Geological Sciences, one of the study’s authors. “Then, in a window of time lasting just a few thousand years, the megafauna population collapsed.” According to Miller, the study results suggest that shortly after the arrival of humans 85 percent of Australia’s megafauna weighing over 100 pounds went extinct. Tellingly, the sediment core analysis also revealed that Australia’s southwest had dense forests 45,000 years ago, much like it does today. A hotbed of biodiversity, these forests make it unlikely that ecosystem change was behind the extinction of the megafauna. “It’s a region with some of the earliest evidence of humans on the continent, and where we would expect a lot of animals to have lived,” Miller explained. “Because of the density of trees and shrubs, it could have been one of their last holdouts some 45,000 years ago. There is no evidence of significant climate change during the time of the megafauna extinction.” Miller suggests that “imperceptible overkill” could have caused the extinction. A study published in 2006 claimed that even a small amount of megafauna hunting, at a rate as low as one juvenile mammal being killed per person per decade, could well have led to a species going extinct within a few hundred years. “The results of this study are of significant interest across the archaeological and Earth science communities and to the general public who remain fascinated by the menagerie of now extinct giant animals that roamed the planet – and the cause of their extinction – as our own species began its persistent colonization of Earth,” said study leader Sander van der Kaars of Monash University. The issue of the cause behind Australian megafauna extinction is likely to remain controversial, however. Just last week a study was published arguing that humans and certain megafauna coexisted for a least 17,000 years in Australia, highlighting just how complicated the extinction process might have been. Image courtesy of Peter Trusler, Monash University]]>