Toba supereruption unveils new insights into early human migration

Modern humans dispersed from Africa multiple times, but the event that led to global expansion occurred less than 100,000 years ago. Some researchers hypothesize that dispersals were restricted to "green corridors" formed during humid intervals when food was abundant and human populations expanded in lockstep with their environments. But a new study in Nature, including ASU researchers Curtis Marean, Christopher Campisano, and Jayde Hirniak, suggests that humans also may have dispersed during arid intervals along "blue highways" created by seasonal rivers. Researchers also found evidence of cooking and stone tools that represent the oldest evidence of archery.

Working in the Horn of Africa, researchers have uncovered evidence showing how early modern humans survived in the wake of the eruption of Toba, one of the largest supervolcanoes in history, some 74,000 years ago. The behavioral flexibility of these people not only helped them live through the supereruption but may have facilitated the later dispersal of modern humans out of Africa and across the rest of the world.

"This study confirms the results from Pinnacle Point in South Africa -- the eruption of Toba may have changed the environment in Africa, but people adapted and survived that eruption-caused environmental change," said Marean, research scientist with the Institute of Human Origins and Foundation Professor with the School of Human Evolution and Social Change.

The team investigated the Shinfa-Metema 1 site in the lowlands of present-day northwestern Ethiopia along the Shinfa River, a tributary of the Blue Nile River.

The supereruption occurred during the middle of the time when the site was occupied and is documented by tiny glass shards whose chemistry matches that of Toba.

Pinpoint timing through cryptotephra

"One of the ground-breaking implications of this study," said Marean, "is that with the new cryptotephra methods developed for our prior study in South Africa, and now applied here to Ethiopia, we can correlate sites across Africa, and perhaps the world, at a resolution of several weeks of time."

Cryptotephra are signature volcanic glass shards that can range from 80-20 microns in size, which is smaller than the diameter of a human hair. To extract these microscopic shards from archaeological sediment requires patience and great attention to detail.

"Searching for cryptotephra at these archaeological sites is like looking for a needle in a haystack, but not knowing if there is even a needle. However, having the ability to correlate sites 5,000 miles apart, and potentially further, to within weeks instead of thousands of years makes it all worth it," said Christopher Campisano, research scientist with the Institute of Human Origins and professor with the School of Human Evolution and Social Change.

"This study, once again," said Campisano, "highlights the importance of the University of Nevada-Las Vegas/Arizona State University team pushing the limits for successfully analyzing extremely low abundance cryptotephra to date and correlate archaeological sites across Africa."

The methods for identifying low abundance cryptotephra at Pinnacle Point were first developed at University of Nevada Las Vegas led by the late Gene Smith and Racheal Johnsen and now carried on at Arizona State University's Sediment and TEphra Preparation (STEP) Lab.

School of Human Evolution and Social Change graduate student Jayde Hirniak led ASU's effort to create its own cryptotephra lab -- the STEP Lab -- working with Campisano and building on methods developed at UNLV. Hirniak also collaborated with cryptotephra labs in the United Kingdom that work with sediment samples preserving hundreds or thousands of glass shards. Now Hirniak's primary expertise is in tephrochronology, which involves the use of volcanic ash to link archaeological and paleoenvironmental records and place them on the same timeline, which was her contribution to this research.

"Our lab at ASU was built to process extremely low abundance cryptotephra horizons (<10 shards per gram) using a highly specialized technique. There are only a few labs in the world with these capabilities," said Hirniak.

Migrations along "blue highways"

Based on isotope geochemistry of the teeth of fossil mammals and ostrich eggshells, they concluded that the site was occupied by humans during a time with long dry seasons on a par with some of the most seasonally arid habitats in East Africa today. Additional findings suggest that when river flows stopped during dry periods, people adapted by hunting animals that came to the remaining waterholes to drink. As waterholes continued to shrink, it became easier to capture fish without any special equipment, and diets shifted more heavily to fish.

Its climatic effects appear to have produced a longer dry season, causing people in the area to rely even more on fish. The shrinking of the waterholes may also have pushed humans to migrate outward in search of more food.

"As people depleted food in and around a given dry season waterhole, they were likely forced to move to new waterholes," said John Kappelman, a UT anthropology and earth and planetary sciences professor and lead author of the study. "Seasonal rivers thus functioned as 'pumps' that siphoned populations out along the channels from one waterhole to another, potentially driving the most recent out-of-Africa dispersal.

The humans who lived at Shinfa-Metema 1 are unlikely to have been members of the group that left Africa. However, the behavioral flexibility that helped them adapt to challenging climatic conditions such as the Toba supereruption was probably a key trait of Middle Stone Age humans that allowed our species to ultimately disperse from Africa and expand across the globe.

The people living in the Shinfa-Metema 1 site hunted a variety of terrestrial animals, from antelope to monkey, as attested to by cut marks on the bones, and apparently cooked their meals as shown by evidence of controlled fire at the site. The most distinctive stone tools are small, symmetrical triangular points. Analyses show that the points are most likely arrowheads that, at 74,000 years in age, represent the oldest evidence of archery.

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Burning candles and fumes from cooking is harmful for people with mild asthma

A cosy set table, a nice steak in the pan, and romantic candlelight may sound like the start of a lovely evening. However, a new study from the Department of Public Health at Aarhus University suggests that you should be cautious about inhaling too much of the cosy atmosphere. Karin Rosenkilde Laursen, a postdoc at the department and co-author of the study, says:

"Our study shows that indoor air pollution caused by fumes from cooking and burning candles can lead to adverse health effects such as irritation and inflammation in young individuals with mild asthma. Among other things, we've found indications of DNA damage and signs of inflammation in the blood."

When we turn on the oven, place a pan on the hob, or light candles, ultrafine particles and gases are produced, which we then inhale. Previous studies have shown that these particles and gases can be detrimental to health. What sets this study apart is that the researchers have focused on the effects on young individuals with mild asthma, aged between 18 and 25, says Karin Rosenkilde Laursen:

"In the study, we observed that even very young individuals with mild asthma can experience discomfort and adverse effects if the room is not adequately ventilated during cooking or when burning candles. Young people are generally fitter and more resilient than older and middle-aged individuals. Therefore, it is concerning that we observed a significant impact from the particles on this particularly young age group."

But not only people diagnosed with asthma need to keep an eye on the indoor climate, she says.

"Even though the study focused on young asthmatics, its findings are interesting and relevant for all of us. Winter is approaching, a time when we tend to light many candles and perhaps are less likely to open doors and windows while cooking. By prioritising a healthier indoor climate, even when we're cosying up indoors, we may be able to help reduce the incidence of serious lung and cardiovascular diseases, as well as cancer."

Karin Rosenkilde Laursen plans to follow up this study with another examining how emissions from cooking and candles affect healthy adults.

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Oldest evidence of the controlled use of fire to cook food, researchers report

A remarkable scientific discovery has been made by researchers from the Hebrew University of Jerusalem (HU), Tel Aviv University (TAU), and Bar-Ilan University (BIU), in collaboration with the Steinhardt Museum of Natural History, Oranim Academic College, the Israel Oceanographic and Limnological Research (IOLR) institution, the Natural History Museum in London, and the Johannes Gutenberg University in Mainz. A close analysis of the remains of a carp-like fish found at the Gesher Benot Ya'aqov (GBY) archaeological site in Israel shows that the fish were cooked roughly 780,000 years ago. Cooking is defined as the ability to process food by controlling the temperature at which it is heated and includes a wide range of methods. Until now, the earliest evidence of cooking dates to approximately 170,000 years ago. The question of when early man began using fire to cook food has been the subject of much scientific discussion for over a century. These findings shed new light on the matter and was published in Nature Ecology and Evolution.

The study was led by a team of researchers: Dr. Irit Zohar, a researcher at TAU's Steinhardt Museum of Natural History and curator of the Beit Margolin Biological Collections at Oranim Academic College, and HU Professor Naama Goren-Inbar, director of the excavation site. The research team also included Dr. Marion Prevost at HU's Institute of Archaeology; Prof. Nira Alperson-Afil at BIU's Department for Israel Studies and Archaeology; Dr. Jens Najorka of the Natural History Museum in London; Dr. Guy Sisma-Ventura of the Israel Oceanographic and Limnological Research Institute; Prof. Thomas Tütken of the Johannes Gutenberg University in Mainz and Prof. Israel Hershkovitz at TAU's Faculty of Medicine.

Dr. Zohar and Dr. Prevost: "This study demonstrates the huge importance of fish in the life of prehistoric humans, for their diet and economic stability. Further, by studying the fish remains found at Gesher Benot Ya'aqob we were able to reconstruct, for the first time, the fish population of the ancient Hula Lake and to show that the lake held fish species that became extinct over time. These species included giant barbs (carp like fish) that reached up to 2 meters in length. The large quantity of fish remains found at the site proves their frequent consumption by early humans, who developed special cooking techniques. These new findings demonstrate not only the importance of freshwater habitats and the fish they contained for the sustenance of prehistoric man, but also illustrate prehistoric humans' ability to control fire in order to cook food, and their understanding the benefits of cooking fish before eating it."

In the study, the researchers focused on pharyngeal teeth (used to grind up hard food such as shells) belonging to fish from the carp family. These teeth were found in large quantities at different archaeological strata at the site. By studying the structure of the crystals that form the teeth enamel (whose size increases through exposure to heat), the researchers were able to prove that the fish caught at the ancient Hula Lake, adjacent to the site, were exposed to temperatures suitable for cooking, and were not simply burned by a spontaneous fire.

Until now, evidence of the use of fire for cooking had been limited to sites that came into use much later than the GBY site -- by some 600,000 years, and ones most are associated with the emergence of our own species, homo sapiens.

Prof. Goren-Inbar added: "The fact that the cooking of fish is evident over such a long and unbroken period of settlement at the site indicates a continuous tradition of cooking food. This is another in a series of discoveries relating to the high cognitive capabilities of the Acheulian hunter-gatherers who were active in the ancient Hula Valley region. These groups were deeply familiar with their environment and the various resources it offered them. Further, it shows they had extensive knowledge of the life cycles of different plant and animal species. Gaining the skill required to cook food marks a significant evolutionary advance, as it provided an additional means for making optimal use of available food resources. It is even possible that cooking was not limited to fish, but also included various types of animals and plants."

Prof. Hershkovitz and Dr. Zohar note that the transition from eating raw food to eating cooked food had dramatic implications for human development and behavior. Eating cooked food reduces the bodily energy required to break down and digest food, allowing other physical systems to develop. It also leads to changes in the structure of the human jaw and skull. This change freed humans from the daily, intensive work of searching for and digesting raw food, providing them free time in which to develop new social and behavioral systems. Some scientists view eating fish as a milestone in the quantum leap in human cognitive evolution, providing a central catalyst for the development of the human brain. They claim that eating fish is what made us human. Even today, it is widely known that the contents of fish flesh, such as omega-3 fatty acids, zinc, iodine and more, contribute greatly to brain development.

The research team believe that the location of freshwater areas, some of them in areas that have long since dried up and become arid deserts, determined the route of the migration of early man from Africa to the Levant and beyond. Not only did these habitats provide drinking water and attracted animals to the area but catching fish in shallow water is a relatively simple and safe task with a very high nutritional reward.

The team posits that exploiting fish in freshwater habitats was the first step on prehistoric humans' route out of Africa. Early man began to eat fish around 2 million years ago but cooking fish -- as found in this study -- represented a real revolution in the Acheulian diet and is an important foundation for understanding the relationship between man, the environment, climate, and migration when attempting to reconstruct the history of early humans.

It should be noted that evidence of the use of fire at the site -- the oldest such evidence in Eurasia -- was identified first by BIU's Prof. Nira Alperson-Afil. "The use of fire is a behavior that characterizes the entire continuum of settlement at the site," she explained. "This affected the spatial organization of the site and the activity conducted there, which revolved around fireplaces." Alperson-Afil's research of fire at the site was revolutionary for its time and showed that the use of fire began hundreds of thousands of years before previously thought.

HU's Goren-Inbar added that the archaeological site of GBY documents a continuum of repeated settlement by groups of hunter-gatherers on the shores of the ancient Hula Lake which lasting tens of thousands of years. "These groups made use of the rich array of resources provided by the ancient Hula Valley and left behind a long settlement continuum with over 20 settlement strata," Goren-Inbar explained. The excavations at the site have uncovered the material culture of these ancient hominins, including flint, basalt, and limestone tools, as well as their food sources, which were characterized by a rich diversity of plant species from the lake and its shores (including fruit, nuts, and seeds) and by many species of land mammals, both medium-sized and large.

Dr. Jens Najorka of the Natural History Museum in London explained: "In this study, we used geochemical methods to identify changes in the size of the tooth enamel crystals, as a result of exposure to different cooking temperatures. When they are burnt by fire, it is easy to identify the dramatic change in the size of the enamel crystals, but it is more difficult to identify the changes caused by cooking at temperatures between 200 and 500 degrees Celsius. The experiments I conducted with Dr. Zohar allowed us to identify the changes caused by cooking at low temperatures. We do not know exactly how the fish were cooked but given the lack of evidence of exposure to high temperatures, it is clear that they were not cooked directly in fire, and were not thrown into a fire as waste or as material for burning."

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Prehistoric feces reveal parasites from feasting at Stonehenge

A new analysis of ancient faeces found at the site of a prehistoric village near Stonehenge has uncovered evidence of the eggs of parasitic worms, suggesting the inhabitants feasted on the internal organs of cattle and fed leftovers to their dogs.

Durrington Walls was a Neolithic settlement situated just 2.8km from Stonehenge, and dating from around 2500 BC, when much of the famous stone monument was constructed. It is believed that the site housed the people who built Stonehenge.

A team of archaeologists led by the University of Cambridge investigated nineteen pieces of ancient faeces, or 'coprolite', found at Durrington Walls and preserved for over 4,500 years. Five of the coprolites (26%) -- one human and four dog -- were found to contain the eggs of parasitic worms.

Researchers say it is the earliest evidence for intestinal parasites in the UK where the host species that produced the faeces has also been identified. The findings are published today in the journal Parasitology.

"This is the first time intestinal parasites have been recovered from Neolithic Britain, and to find them in the environment of Stonehenge is really something," said study lead author Dr Piers Mitchell from Cambridge's Department of Archaeology.

"The type of parasites we find are compatible with previous evidence for winter feasting on animals during the building of Stonehenge," he said.

Four of the coprolites, including the human one, contained the eggs of capillariid worms, identified in part by their lemon shape.

While the many types of capillariid around the world infect a wide range of animals, on the rare occasion that a European species infects humans the eggs get lodged in the liver and don't appear in stool.

The evidence of capillariid eggs in human faeces indicates that the person had eaten the raw or undercooked lungs or liver from an already infected animal, resulting in the parasite's eggs passing straight through the body.

During excavations of the main 'midden' -- or dung and refuse heap -- at Durrington Walls, archaeologists uncovered pottery and stone tools along with over 38,000 animal bones. Some 90% of the bones were from pigs, with less than 10% from cows. This is also where the partially mineralised faeces used in the study were found.

"As capillariid worms can infect cattle and other ruminants, it seems that cows may have been the most likely source of the parasite eggs," said Mitchell.

Previous isotopic analyses of cow teeth from Durrington Walls suggest that some cattle were herded almost 100km from Devon or Wales to the site for large-scale feasting. Patterns of butchery previously identified on cattle bones from the site suggest beef was primarily chopped for stewing, and bone marrow was extracted.

"Finding the eggs of capillariid worms in both human and dog coprolites indicates that the people had been eating the internal organs of infected animals, and also fed the leftovers to their dogs," said co-author Evilena Anastasiou, who assisted with the research while at Cambridge.

To determine whether the coprolites excavated from the midden were from human or animal faeces, they were analysed for sterols and bile acids at the National Environment Isotope Facility at the University of Bristol.

One of the coprolites belonging to a dog contained the eggs of fish tapeworm, indicating it had previously eaten raw freshwater fish to become infected. However, no other evidence of fish consumption, such as bones, has been found at the site.

"Durrington Walls was occupied on a largely seasonal basis, mainly in winter periods. The dog probably arrived already infected with the parasite," said Dr Piers Mitchell.

"Isotopic studies of cow bones at the site suggests they came from regions across southern Britain, which was likely also true of the people who lived and worked there."

The dates for Durrington Walls match those for stage two of the construction of Stonehenge, when the world-famous 'trilithons' -- two massive vertical stones supporting a third horizontal stone -- were erected, most likely by the seasonal residents of this nearby settlement.

While Durrington Walls was a place of feasting and habitation, as evidenced by the pottery and vast number of animal bones, Stonehenge itself was not, with little found to suggest people lived or ate there en masse.

Prof Mike Parker Pearson from UCL's Institute of Archaeology, who excavated Durrington Walls between 2005 and 2007, added: "This new evidence tells us something new about the people who came here for winter feasts during the construction of Stonehenge."

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Pollution from cooking emissions hangs in the air

Organic aerosols -- such as those released in cooking -- may stay in the atmosphere for several days, because of nanostructures formed by fatty acids as they are released into the air.

By identifying the processes which control how these aerosols are transformed in the atmosphere, scientists will be able to better understand and predict their impact on the environment and the climate.

Experts at the Universities of Birmingham and Bath have used instruments at the Diamond Light Source and the Central Laser Facility, both based at the Harwell Campus in Oxford, to probe the behaviour of thin films of oleic acid -- an unsaturated fatty acid commonly released when cooking.

In the study, published in Atmospheric Chemistry and Physics, they were able to analyse the particular molecular properties that control how rapidly aerosol emissions can be broken down in the atmosphere.

Then, using a theoretical model combined with experimental data the team was able to predict the amount of time aerosols generated from cooking may hang around in the environment.

These types of aerosols have long been associated with poor air quality in urban areas, but their impact on human-made climate change is hard to gauge. That's because of the diverse range of molecules found within aerosols, and their varying interactions with the environment.

By identifying the nanostructure of molecules emitted during cooking that slows down the break-up of organic aerosols, it becomes possible to model how they are transported and dispersed into the atmosphere.

Lead author Dr Christian Pfrang, of the University of Birmingham's School of Geography, Earth and Environmental Sciences, said: "Cooking aerosols account for up to 10 per cent of particulate matter (PM) emissions in the UK. Finding accurate ways to predict their behaviour will give us much more precise ways to also assess their contribution to climate change."

Co-author Dr Adam Squires, of the University of Bath, said: "We're increasingly finding out how molecules like these fatty acids from cooking can organise themselves into bilayers and other regular shapes and stacks within aerosol droplets that float in the air, and how this completely changes how fast they degrade, how long they persist in the atmosphere, and how they affect pollution and weather."

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Where does the special scent of thyme and oregano come from?

Thyme and oregano are not only popular herbs for cooking, but also valuable medicinal plants. Their essential oils contain thymol and carvacrol which impart the typical flavors and are medically important. A team from Martin Luther University Halle-Wittenberg (MLU) and Purdue University in the USA has now fully identified how the plants produce these two substances. The results could simplify the breeding process and improve the pharmaceutical value of thyme and oregano. The study appears in the journal Proceedings of the National Academy of Sciences.

Thymol, which is mainly extracted from thyme, has secretolytic, antibacterial and antispasmodic properties. The plant is therefore often used in tea for colds, cough syrups and as an herbal remedy for bronchitis. In contrast, oregano contains particularly high levels of carvacrol, which has similar properties. Its smell is often associated with pizza sauce and other Mediterranean dishes. Both substances are chemically closely related and are produced by thyme and oregano in multi-stage processes. "It's like a production line in a factory: Every step needs to be coordinated and the desired product only emerges when the steps are carried out in the right order," explains Professor Jörg Degenhardt from the Institute of Pharmacy at MLU. Instead of machines, specific biomolecules -- enzymes -- carry out this work in special glands on the surface of the leaves.

Together with researchers from Purdue University in the USA, the team in Halle decoded the individual production steps, thereby solving a decades-old mystery. "For a long time it was assumed that p-Cymene was an intermediate product of thymol and carvacrol synthesis. However, it was chemically not feasible for thymol or carvacrol to ultimately be produced from this substance," says Degenhardt. In fact, normal production of the two substances does not produce any p-Cymene at all, but rather an extremely unstable intermediate product. "This is only present for a few moments in the plant cells, which is why observing it is so difficult. However, it represents the hitherto missing step in the synthesis of the two substances," says Degenhardt. The processes start out the same for both thymol and carvacrol; only in step four do different enzymes that produce the respective substances come into play. In a fifth step, thymol and carvacrol can be further converted to thymohydroquinone and thymoquinone, which have anti-inflammatory and anti-tumour effects.

The researchers were also able to use these new findings to genetically reprogramme a species of tobacco, the model plant N. benthamiana, to produce thymol. "Even though this only happened in small quantities, it meant that we were able to fully understand the synthesis pathways and the associated enzymes," summarises Degenhardt.

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