Category: Fossils & Ruins

Categories
Earth & Climate Energy & Matter Fossils & Ruins Researcher news SMU In The News

The Washington Post: Oil and gas industry is causing Texas earthquakes, a ‘landmark’ study suggests

The study authors took a different approach in the new work — they hunted for deformed faults below Texas.

The Washington Post covered the landmark earthquake research of a team of SMU geophysicists led by SMU Associate Professor Beatrice Magnani in the SMU Department of Earth Sciences.

The researchers tapped seismic data to analyze earthquakes in Texas over the past decade.

The results of the analysis showed that human activity is causing the earthquakes as a result of movement in faults that have been silent for at least 300 million years, until recent injection of oil and gas wastewater.

The article by journalist Ben Guarino, “Oil and gas industry is causing Texas earthquakes, a ‘landmark’ study suggests,” published Nov. 24, 2017.

Read the full story.

EXCERPT:

By Ben Guarino
The Washington Post
An unnatural number of earthquakes hit Texas in the past decade, and the region’s seismic activity is increasing. In 2008, two earthquakes stronger than magnitude 3 struck the state. Eight years later, 12 did.

Natural forces trigger most earthquakes. But humans are causing earthquakes, too, with mining and dam construction the most frequent suspects. There has been a recent increase in natural gas extraction — including fracking, or hydraulic fracturing, but other techniques as well — which produces a lot of wastewater. To get rid of it, the water is injected deep into the ground. When wastewater works its way into dormant faults, the thinking goes, the water’s pressure nudges the ancient cracks. Pent-up tectonic stress releases and the ground shakes.

But for any given earthquake, it is virtually impossible to tell whether humans or nature triggered the quake. There are no known characteristics of a quake, not in magnitude nor in the shape of its seismic waves, that provide hints to its origins.

“It’s been a head-scratching period for scientists,” said Maria Beatrice Magnani, who studies earthquakes at Southern Methodist University in Dallas. Along with a team of researchers at the U.S. Geological Survey, Magnani, an author of a new report published Friday in the journal Science Advances, attempted to better identify what has been causing the rash of Texas quakes.

A cluster of earthquakes around a drilling project can, at best, suggest a relationship. “The main approach has been to correlate the location to where there has been human activity,” said Michael Blanpied, a USGS geophysicist and co-author of the new study.

Read the full story.

Categories
Earth & Climate Fossils & Ruins Plants & Animals Student researchers Subfeature

Prehistoric puzzle settled: carbon dioxide link to global warming 22 million years ago

The modern link between high carbon dioxide levels and climate change didn’t appear to hold true for a time interval about 22 million years ago; but now a new study has found the link does indeed exist.

Fossil leaves from Africa have resolved a prehistoric climate puzzle — and also confirm the link between carbon dioxide in the atmosphere and global warming.

Research until now has produced a variety of results and conflicting data that have cast doubt on the link between high carbon dioxide levels and climate change for a time interval about 22 million years ago.

But a new study has found the link does indeed exist for that prehistoric time period, say researchers at Southern Methodist University, Dallas.

The finding will help scientists understand how recent and future increases in the concentration of atmospheric carbon dioxide may impact the future of our planet, say the SMU researchers.

The discovery comes from new biochemical analyses of fossil leaves from plants that grew on Earth 27 million years ago and 22 million years ago, said geologist Tekie Tesfamichael, lead scientist on the research.

The new analyses confirm research about modern climate — that global temperatures rise and fall with increases and decreases in carbon dioxide in our atmosphere — but in this case even in prehistoric times, according to the SMU-led international research team.

Carbon dioxide is a gas that is normally present in the Earth’s atmosphere, even millions of years ago. It’s dubbed a greenhouse gas because greater concentrations cause the overall temperature of Earth’s atmosphere to rise, as happens in a greenhouse with lots of sunlight.

Recently greenhouse gas increases have caused global warming, which is melting glaciers, sparking extreme weather variability and causing sea levels to rise.

The new SMU discovery that carbon dioxide behaved in the same manner millions of years ago that it does today has significant implications for the future. The finding suggests the pairing of carbon dioxide and global warming that is seen today also holds true for the future if carbon dioxide levels continue to rise as they have been, said Tesfamichael.

“The more we understand about the relationship between atmospheric carbon dioxide concentrations and global temperature in the past, the more we can plan for changes ahead,” said Tesfamichael, an SMU postdoctoral fellow in Earth Sciences.

“Previous work reported a variety of results and conflicting data about carbon dioxide concentrations at the two intervals of time that we studied,” he said. “But tighter control on the age of our fossils helped us to address whether or not atmospheric carbon dioxide concentration corresponded to warming — which itself is independently well-documented in geochemical studies of marine fossils in ocean sediments.”

The researchers reported their findings in Geology, the scientific journal of the Geological Society of America. The article is “Settling the issue of ‘decoupling’ between atmospheric carbon dioxide and global temperature: [CO2]atm reconstructions across the warming Paleogene-Neogene divide.”

Co-authors from the Roy M. Huffington Department of Earth Sciences in Dedman College are professors Bonnie Jacobs, an expert in paleobotany and paleoclimate, and Neil J. Tabor, an expert in sedimentology and sedimentary geochemistry.

Other co-authors are Lauren Michel, Tennessee Technological University; Ellen Currano, University of Wyoming; Mulugeta Feseha, Addis Ababa University; Richard Barclay, Smithsonian Institution; John Kappelman, University of Texas; and Mark Schmitz, Boise State University.

Discovery of rare, well-preserved fossil leaves enables finding
The findings were possible thanks to the rare discovery of two sites with extraordinarily well-preserved fossil leaves of flowering plants from the Ethiopian Highlands of eastern Africa.

Such well-preserved fossil leaves are a rarity, Tesfamichael said.

“Finding two sites with great preservation in the same geographic region from two important time intervals was very fortunate, as this enabled us to address the question we had about the relationship between atmospheric carbon dioxide concentration and global temperatures,” he said.

Scientists know that variations in the concentration of atmospheric carbon dioxide affect carbon fixation in leaves during photosynthesis. This causes leaves to develop anatomical and physiological changes such as the frequency and size of stomata — the pores on the surface of a leaf through which carbon passes.

Scientists can measure those attributes, among others, in fossil leaves, so that leaf fossils can be used as proxies for Earth’s atmospheric carbon dioxide history.

The sites producing the leaves for the SMU study were discovered separately in years past, but major fossil collections were produced through field work coordinated by the SMU research team and their co-authors, who have been collaborating on this project for several years.

The work has had funding from the National Science Foundation, The National Geographic Committee for Research and Exploration, the SMU Ford Fellowship Program, SMU Research Council, the Institute for the Study of Earth and Man, and the Dallas Paleontological Society Frank Crane Scholarship.

The fossils are housed permanently in the collections at the National Museum of Ethiopia in Addis Ababa. Institutional and governmental support came from the National Museum of Ethiopia, the Authority for Research and Conservation of Cultural Heritage, and Addis Ababa University.

Previous studies firmly established a temperature difference
One of the sites dates to the late Oligocene Epoch, and the other to the early Miocene.

Previous studies that measured ocean temperatures from around the world for the two intervals have firmly established a temperature difference on Earth between the two times, with one much warmer than the other. So the SMU study sought to measure the levels of carbon dioxide for the two time periods.

For the SMU analyses, fossil leaves of a single species were collected from the 27 million-year-old late Oligocene site. The leaves had been deposited during prehistoric times in the area of Chilga in northwest Ethiopia most likely at a river bank. The Earth’s climate during the late Oligocene may have been somewhat warmer than today, although glaciers were forming on Antarctica. The SMU study found carbon dioxide levels, on average, around 390 parts per million, about what it is on Earth today.

Fossil leaves of the 22 million-year-old species from the early Miocene were collected from ancient lake deposits, now a rock called shale, from the modern-day Mush Valley in central Ethiopia. The early Miocene climate at that time was warmer than the late Oligocene and likewise the SMU study found higher carbon dioxide levels. Atmospheric carbon dioxide was about 870 parts per million, double what it is on Earth today.

The SMU study confirmed a relationship between carbon dioxide and temperature during the late Oligocene and early Miocene.

Paleoclimate data can help predict our planet’s future climate
While carbon dioxide isn’t the only factor affecting Earth’s climate or global mean temperature, it is widely considered by scientists among the most significant. Much is known about climate change and global warming, but questions still remain.

“One of those is ‘What’s the sensitivity of the Earth’s temperature to carbon dioxide concentration? Is it very sensitive? Is it not so sensitive?’ Estimating temperature and carbon dioxide concentrations for times in the past can help find the answer to that question,” Jacobs said. “There’s a lot of work on paleoclimate in general, but not as much on the relationship between carbon dioxide and temperature.”

The finding is an important one.

“The amount of temperature change during this interval is approximately within the range of the temperature change that is estimated from climate models for our next century given a doubling of carbon dioxide concentration since the industrial revolution,” Jacobs said.

With the new model reaffirming the prehistoric relationship, scientists can look now at related questions, said climate change scientist Lauren Michel, who worked on the study as a post-doctoral researcher at SMU.

“Answering questions about the rate of change and which factors changed first, for example, will ultimately give a clearer picture of the Earth’s climate change patterns,” Michel said. “I think it is valuable to understand the relationship of greenhouse gases and climate factors represented in the rock record so we can have a better idea of what we can expect in the future and how we can prepare for that.”

SMU study confirms relationship that previous methods overlooked
Previous studies found little to no correlation between temperature and carbon dioxide for the late Oligocene and early Miocene. That has puzzled paleoclimate researchers for at least a decade.

“We have a good test-case scenario with these well-preserved plants from both time slices, where we know one time slice, with higher levels of carbon dioxide, was a warmer climate globally than the other,” Tesfamichael said.

“It’s been a puzzle as to why the previous methods found no relationship, or an inverse correlation,” he said. “We think it’s for lack of the well-dated proxy — such as our fossil leaves from two precise times in the same region — which deliver a reliable answer. Or, perhaps the models themselves needed improvement.”

Previous studies used methodologies that differed from the SMU study, although all methods (proxies) incorporate some aspects of what is known about living organisms and how they interact with atmospheric carbon dioxide.

Some studies rely on biochemical modeling of the relationship between single-celled marine fossils and atmospheric carbon dioxide, and others rely on the relationship between stomata and atmospheric carbon dioxide concentration observed in the living relatives of particular fossil plant species.

“Each method has its assumptions,” said Tesfamichael. “We will see if our results hold up with further studies of this time interval using the same methodology we used.” — Margaret Allen, SMU

Categories
Culture, Society & Family Fossils & Ruins Researcher news Subfeature

Prehistoric humans formed complex mating networks to avoid inbreeding

An individual buried at Snugger, whose remains were some of those whose complete genomes were sequenced. (Credit: Libor Balák, Anthropark)

A new study has sequenced the genomes of individuals from an ancient burial site in Russia and discovered that they were, at most, first cousins, indicating that they had developed sexual partnerships beyond their immediate social and family group.

A new study has identified when humans transitioned from simple systems designed to minimize inbreeding to more complex ones suitable for hunter-gatherer societies.

The study findings are reported in the journal Science and demonstrate that, by at least 34,000 years ago, human hunter-gatherer groups had developed sophisticated social and mating networks that minimized inbreeding.

The study examined genetic information from the remains of modern humans who lived during the early part of the Upper Palaeolithic, a period when modern humans from Africa first colonized western Eurasia, eventually displacing the Neanderthals who lived there before.

The results suggest that people deliberately sought partners beyond their immediate family, and that they were probably connected to a wider network of groups from within which mates were chosen, thus avoiding inbreeding.

The research was carried out by an international team of academics, led by the University of Cambridge, U.K., and the University of Copenhagen, Denmark. The team included SMU archaeologist David J. Meltzer, whose expertise includes the First People in the Americas.

The researchers sequenced the genomes of four individuals from Sunghir, a famous Upper Palaeolithic site in Russia, which was inhabited about 34,000 years ago.

The article, “Ancient genomes show social and reproductive behavior of early Upper Paleolithic foragers,” is published in the Oct. 5, 2017 issue of Science.

Complex mating systems may partly explain modern human survival
Among recent hunter-gatherers, the exchange of mates between groups is embedded into a cultural system of rules, ceremonies and rituals. The symbolism, complexity and time invested in the extraordinarily rich objects and jewellery found in the Sunghir burials, as well as the burials themselves, suggest that these early human societies symbolically marked major events in the life of individuals and their community in ways that foreshadow modern rituals and ceremonies — birth, marriage, death, shared ancestry, shared cultures.

The study’s authors also hint that the early development of more complex mating systems may at least partly explain why modern humans proved successful while other, rival species, such as Neanderthals, did not. More ancient genomic information from both early humans and Neanderthals is needed to test this idea.

The human fossils buried at Sunghir are a unique source of information about early modern human societies of western Eurasia. Sunghir preserves two contemporaneous burials – that of an adult man, and that of two children buried together and which includes the symbolically modified remains of another adult.

To the researchers’ surprise, however, these individuals were not closely related in genetic terms; at the very most, they were second cousins. This is true even for the two children who were buried head-to-head in the same grave.

“What this means is that people in the Upper Palaeolithic, who were living in tiny groups, understood the importance of avoiding inbreeding,” said Eske Willerslev, a professor at St John’s College and the University of Copenhagen, who was senior author on the study. “The data that we have suggest that it was being purposely avoided. This means that they must have developed a system for this purpose. If the small hunter and gathering bands were mixing at random, we would see much greater evidence of inbreeding than we have here.”

Early human societies changed ancestral mating system
The small family bands were likely interconnected within larger networks, facilitating the exchange of peoples between bands in order to maintain diversity, said Martin Sikora, a professor at the Centre for GeoGenetics at the University of Copenhagen.

Most non-human primate societies are organized around single-sex kin (matrilines or patrilines), where one of the sexes remains resident and the other migrates to another group, thus minimizing inbreeding. At some point, early human societies changed the ancestral mating system into one in which a large number of the individuals that form small resident/foraging units are non-kin, where the relations among units that exchange mating partners are formalized through complex cultural systems.

In at least one Neanderthal case, an individual from the Altai Mountains who died about 50,000 years ago, inbreeding was not avoided, suggesting that the modern human cultural systems that allows to decouple the size of the resident community from the danger of inbreeding was not in place. This leads the researchers to speculate that an early, systematic approach to preventing inbreeding may have helped modern humans to thrive in relation to with other hominins.

This should be treated with caution, however.

“We don’t know why the Altai Neanderthal groups were inbred,” Sikora said. “Maybe they were isolated and that was the only option; or maybe they really did fail to develop a network of connections. We will need more genomic data of diverse Neanderthal populations to be sure.”

Upper Palaeolithic human groups sustained very small group sizes
The researchers were able to sequence the complete genomes of all four individuals found within the two graves at Sunghir. These data were compared with information on both modern and ancient human genomes from across the world.

They found that the four individuals studied were genetically no closer than second cousins, while the adult femur filled with red ochre found in the youngsters’ grave would have belonged to an individual no closer than great-great grandfather of the boys. “This goes against what many would have predicted,” Willerslev said. “I think many researchers had assumed that the people of Sunghir were very closely related, especially the two youngsters from the same grave.”

The people at Sunghir may have been part of a network similar to that of modern day hunter-gatherers, such as Aboriginal Australians and some historical Native American societies. Like their Upper Palaeolithic ancestors, these societies lived in fairly small groups of some 25 people, but they were also connected to a larger community of perhaps 200 people, within which there were rules governing with whom individuals can form partnerships.

“The results from Sunghir show that Upper Palaeolithic human groups could sustain very small group sizes by embedding them in a wide social network of other groups maintained by sophisticated cultural systems,” said Marta Mirazón Lahr, a professor at the University of Cambridge.

Willerslev also highlights a possible link with the unusual sophistication of the ornaments and cultural objects found at Sunghir. Such band-specific cultural expressions may have been used to signal who are “we” versus who are “they,” and thus a means of reinforcing a shared identity built on marriage exchange across foraging units. The number and sophistication of personal ornaments and artefacts found at Sunghir are exceptional even among other modern human burials, and not found among Neanderthals and other hominins.

“The ornamentation is incredible and there is no evidence of anything like that with other hominins,” Willerslev added. “When you put the evidence together, it seems to be telling us about the really big questions: what made these people who they were as a species, and who we are as a result.”

Ancient genomics throw light on aspects of social life
These results show the power of ancient genomics to throw light on aspects of social life among early humans, and pave the way for further studies to explore variation in social and demographic strategies in prehistoric socieities.

“Much of human evolution is about changes in our social and cultural behavior, and the impact this has had on our success as a species. This study takes us a step further toward pinpointing when and why the things that make humans unique evolved,” said Robert Foley, a professor at the University of Cambridge.

Meltzer is Henderson-Morrison Professor of Prehistory in the SMU Department of Anthropology in Dedman College. As a scientist who studies how people first came to inhabit North America, Meltzer in 2009 was elected a member of the National Academy of Sciences in recognition for his achievements in original scientific research. In 2013 he was elected to the American Academy of Arts and Sciences. — University of Cambridge, SMU

Categories
Culture, Society & Family Fossils & Ruins Researcher news Technology

A composite window into human history

Excavated dwellings in the stone-built Neolithic settlement of Skara Brae in the Orkney archipelago of Scotland. (John Burka)

Better integration of ancient DNA studies with archaeology promises deeper insights.

DNA testing alone of ancient human remains can’t resolve questions about past societies.

It’s time for geneticists and archaeologists to collaborate more fully in the face of ever greater advancements in ancient DNA research, according to SMU archaeologist David J. Meltzer and his colleagues in a recent article in the scientific journal Science.

The authors write in “A composite window into human history” that over the past decade, DNA testing of ancient human remains has become a valuable tool for studying and understanding past human population histories.

Most notably, for example, is how sequencing of ancient genomes resolved the dispute over our species’ evolutionary relationship with Neanderthals, the authors point out.

Even so, the authors caution that collaboration with archaeologists is key for scientific accuracy as well as navigating ethical implications.

Archaeologists know from the study of artifacts that it isn’t always the case that people who share material culture traits were likewise part of the same biological population.

“One can have similar traits without relatedness, and relatedness without similarity in traits,” say the authors in the article.

At the same time, where there is biological relatedness, cultural relatedness can’t be assumed, nor can language groups indicate that biological populations, material assemblages or even social units are related.

“Geneticists are often keen to use ancient DNA to understand the causes and mechanisms of demographic and cultural change,” the authors write. “But archaeologists long ago abandoned the idea that migrations or encounters between populations are a necessary or sufficient explanation of cultural change.”

The authors make the point that understanding population movements requires broad investigation of many factors, including environmental and social contexts, timing and logistics, how new resources and landscapes were managed, and the transfer of cultural knowledge.

“Hence, it requires evidence for archaeology, paleoecology and other fields to supplement and complement ancient DNA data,” the authors write. “And that entails effective collaboration, one that goes beyond archaeologists serving as passive sample providers.”

Meltzer is Henderson-Morrison Professor of Prehistory in the SMU Department of Anthropology in Dedman College. As a scientist who studies how people first came to inhabit North America, Meltzer in 2009 was elected a member of the National Academy of Sciences in recognition for his achievements in original scientific research. In 2013 he was elected to the American Academy of Arts and Sciences.

Co-authors on the perspective piece with Meltzer were Niels N. Johannsen, Aarhus University, Denmark; Greger Larson, University of Oxford; and Marc Vader Linden, University College London.

Categories
Culture, Society & Family Feature Fossils & Ruins Researcher news SMU In The News

Sapiens: Why the Famous Folsom Point Isn’t a Smoking Gun

A Folsom spear point was discovered between the ribs of an extinct species of bison — but was it really proof that humans had killed the animal?

A Folsom spear point was discovered between the ribs of an extinct species of bison — but was it really proof that humans had killed the animal?

The research into the arrival of how and when people first arrived in North America by noted SMU archaeologist David J. Meltzer was covered in the online anthropology magazine Sapiens in a column by Stephen E. Nash, science historian and archaeologist at the Denver Museum of Nature & Science.

The article, Why the Famous Folsom Point Isn’t a Smoking Gun, published Aug. 29, 2017.

Meltzer, a member of the National Academy of Sciences and Henderson-Morrison Professor of Prehistory in SMU’s Dedman College of Humanities and Sciences, conducts original research into the origins, antiquity and adaptations of the first Americans.

Paleoindians colonized the North American continent at the end of the Ice Age. Meltzer focuses on how those hunter-gatherers met the challenges of moving across and adapting to the vast, ecologically diverse landscape of Late Glacial North America during a time of significant climate change.

Meltzer’s archaeology and history research has been supported by grants from the National Geographic Society, the National Science Foundation, The Potts and Sibley Foundation and the Smithsonian Institution. In 1996, he received a research endowment from Joseph and Ruth Cramer to establish the Quest Archaeological Research Program at SMU, which will support in perpetuity research on the earliest occupants of North America.

Read the full story.

EXCERPT:

By Stephen E. Nash
Sapiens
Remember the iconic Folsom point? The one that I said, in my last post, changed the future of archaeology?

To recap: On August 29, 1927, paleontologists from the Colorado Museum of Natural History (renamed the Denver Museum of Nature & Science in 2000) discovered a stone projectile point embedded in the ribs of an extinct form of bison.

After making that discovery in the field, the researchers left the point sitting where it was and immediately sent out a call to their colleagues to come to northeastern New Mexico to see it for themselves. Within two weeks a number of well-known scientists had visited the site, seen the point in position, and established a scientific consensus: Native Americans lived and hunted in North America during the end of the last Ice Age, about 12,000 years ago, far earlier than they were previously thought to be here.

It turns out, though, that the story at the Folsom Site was more complicated than researchers initially believed. So what has changed since 1927? The latest part of the story began 20 years ago.

In 1997, David Meltzer, an archaeologist at Southern Methodist University who studies “Paleoindians,” the earliest inhabitants of North America, began a three-year project at the Folsom Site to reassess and re-excavate the site using modern tools and techniques—which were not available in the 1920s. His goal was to better understand how, and under what conditions, the Folsom Site formed. Meltzer and his team used now-standard excavation-control techniques to record their findings in three-dimensional space and to determine if any unexcavated areas of the site could be found. In so doing, they hoped to find evidence of the Paleoindian campsite that might have been associated with the main bison-kill and butchering site.

As a result of Meltzer’s research, we now know that the bison-kill event occurred in the fall. How do we know? Bison reproduce, give birth, and grow up on a reasonably predictable annual cycle. Meltzer and his colleagues analyzed dental eruption patterns on excavated bison teeth to determine the season of the kill.

The archaeologists also determined that Folsom hunters were experts at their job, having systematically killed and butchered at least 32 bison at the site.

Read the full story.