0000-0001-5280-6944As we continue to reflect on and celebrate PLOS ONE’s 10th anniversary, we bring you the next in our Meet the Editors series, interviewing Michael Petraglia who became an Editorial Board Member in late 2006.
Unidentified remains found in the English countryside and all signs point to the untimely death of a young man. Researchers examined the bones of a supposed victim, which showed signs of leprosy, to search for clues about the arrival of … Continue reading
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Even though our favorite pet dogs are now well-domesticated, we can still catch glimpses of their primal past when we watch them devour a bone or hunt those pesky squirrels. Sadly, new research shows that the status of dogs in … Continue reading
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We’ve all heard the story: dim-witted Neanderthals couldn’t quite keep up with our intelligent modern human ancestors, leading to their eventual downfall and disappearance from the world we know now. Apparently they needed more brain space for their eyes. The authors of a recent PLOS ONE paper are digging into the ideas behind this perception, and take a closer look at eleven common hypotheses for the demise of the Neanderthals, comparing each to the latest research in this field to convince us that Neanderthals weren’t the simpletons we’ve made them out to be.
The authors tackled ideas like the Neanderthal’s capacity for language and innovative ability, both often described as possible weaknesses leading to their decline. Analyzing the published research on each topic, they found that archaeologists often used their finds to “build scenarios” that agreed with the running theories of human superiority, and that some long-held truths have now been challenged by recent discoveries and ongoing research at the same excavation sites.
As one example, researchers who found shell beads and pieces of ochre and manganese in South Africa—used as pigments—claimed them as evidence of the use of structured language in anatomically modern humans. While we can only guess when linking items like these to the presence of language, new findings at Neanderthal sites indicate that they also decorated objects with paints and created personal ornaments using feathers and claws. Whatever the anatomically modern humans were doing in South Africa, Neanderthals were also doing in Europe around the same time, negating the claim that this ability may have provided the anatomically modern humans with better survival prospects once they arrived in Europe.
Another set of South African artifacts led the archaeological community to believe that anatomically modern humans were capable of rapidly improving on their own technology, keeping them ahead of their Neanderthal contemporaries. Two generations of tools, created during the Stillbay and Howiesons Poort periods, were originally believed to have evolved in phases shorter than 10,000 years—a drop in the bucket compared to the Neanderthals’ use of certain tools, unchanged, for 200,000 years. However, new findings suggest that the Stillbay and Howiesons Poort periods lasted much longer than previously thought, meaning that the anatomically modern humans may not have been the great visionaries we had assumed. Additionally, while Neanderthals were not thought capable of crafting the adhesives used by anatomically modern humans to assemble weapons and tools, it is now known that they did, purifying plant resin through an intricate distillation process.
We’re all living proof that anatomically modern humans survived in the end. Perhaps in an effort to flatter our predecessors, we have been holding on to dated hypotheses and ignoring recent evidence showing that Neanderthals were capable of a lot more (and perhaps the anatomically modern humans of a lot less) skill-wise than previously believed. Genetic studies continue to support the idea that anatomically modern humans and Neanderthals interbred and show that the genome of modern humans with Asian or European ancestry contains nearly 2% Neanderthal genes, a substantial quantity considering 40,000 years and 2000 generations have passed since they ceased to exist. These genes may have helped modern humans adjust to life outside of Africa, possibly aiding in the development of our immune system and variation in skin color. Researchers believe that the concentration of Neanderthal genes in modern humans was once much higher, but genetic patterns in modern humans show that hybrid Neanderthal-Human males may have been sterile, leaving no opportunity for their genes to be passed to the next generation.
So, while they may not walk among us today, we have Neanderthals to thank for some major adaptations that allowed us to thrive and spread across the planet. Too bad they’re not here to see the wonderful things we were able to accomplish with their help.
Citation: Villa P, Roebroeks W (2014) Neandertal Demise: An Archaeological Analysis of the Modern Human Superiority Complex. PLoS ONE 9(4): e96424. doi:10.1371/journal.pone.0096424
Image 1: Neandertaler im Museum from Wikimedia Commons
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With more than 7.1 billion people living across the globe, cities house more than 50% of the world’s population. The United Nations Population Fund projects that by 2030 more than 5 billion people will live in cities across the world. The Global Heath Observatory, a program run by the World Health Organization, predicts that by 2050, 7 out of 10 people will live in cities, compared to 2 of 10 just 100 years ago.
Recently, researchers developed what is called “urban scaling theory” to mathematically explain how modern cities behave in predictable ways, despite their unprecedented growth. Recent work in urban scaling research considers cities “social reactors”. In other words, the bigger the city, the more people and more opportunity for social interaction. Think for a moment about the social interactions that occur just on the block outside of your local coffee shop; now multiply those interactions by millions. Cities magnify the number of interactions, increasing both social and economic productivity and, ultimately, encouraging their own growth.
The authors of a recent PLOS ONE paper sought to determine whether ancient cities “behaved” in predictable patterns similar to their modern counterparts. To do so, they developed mathematical models and tested them on archaeological settlements across the Pre-Hispanic Basin of Mexico (BOM, approximated by the red square in the figure below). Based on their findings, they suggest that the principles of settlement organization, which dictate city growth, were very much the same then as they are now, and may be consistent over time.
To test their predictions, the researchers analyzed archaeological data from over 1,500 sites in the BOM, previously surveyed in the 60s and 70s by researchers from the University of Michigan and Penn State.
Using low-altitude aerial photographs and primary survey reports from the original surveyors, the researchers organized the following data from approximately 4,000 sites: the settled area, the average density of potsherds—broken pieces of ceramic material—within it, the count and total surface area of domestic architectural mounds, the settlement type, the estimated population, and the time period.
The researchers were interested in examining areas of the BOM that enabled social interaction between residents, so they excluded site types that did not allow social interaction, for example, isolated ceremonial centers, quarries, and salt mounds. They then grouped the remaining 1,500 sites into both chronological groups and size groups. For chronological grouping, each site was assigned to one of four time periods: the Formative period (1150 B.C.E.–150 B.C.E.), the Classic period (150 B.C.E.–650 C.E.), the Toltec period (650–1200 C.E.), and the Aztec period (1200-1519 C.E.). By the Aztec period, the area had developed from amorphous rural settlements to booming metropolises comprising over 200,000 people.
For site grouping, settlements greater than 5,000 people were categorized differently than smaller settlements. In the figure above, panel B denotes settlements dating to the Formative period (1150 B.C.E.–150 B.C.E.), and panel C, settlements dating to the Aztec period (1200-1519 C.E.).
After separating the data into both chronological groups and size groups, the researchers applied their mathematical models and tested their predictions about urban growth in the settlements of the BOM. One aspect of city development assessed by the researchers was the evolution of defined networks of roads and canals in growing cities. Because roads act as conduits, directly influencing social interaction—much like the roads leading to the aforementioned coffee shop—growing cities develop increasingly defined networks to connect social hubs to one another.
Take, for example, the figure below, which displays both a city in an early stage (panel A) and later (panel B) of growth:
Panel A shows the early, or Amorphous Settlement Model, displaying a small settlement easily accessible to the individual via walking, and thus negating the necessity for clearly defined networks of roads. Panel B, on the other hand, shows the Networked Settlement Model, an infrastructure-dense area where networks are clearly defined to accommodate the increased size of the city and density of the residents. Larger cities analyzed by the authors, like Teotihuacan of the Classic period and Tenochtitlán of the Aztec period, epitomize the Networked Settlement Model with its organized network of roads and canals. The findings from the BOM echo the earlier-stated notion that, like their modern counterparts, ancient cities may have acted as “social reactors”, in part by facilitating an increasingly defined network of roads, themselves directly influencing the ability of residents to socially interact.
Scientists use urban scaling theory to show that population and social phenomena follow distinct, mathematical patterns over time. By developing mathematical models to predict measurable changes in city growth, these researchers applied the same patterns to ancient cities and concluded that the development of settlements over time in the BOM seem analogous to those observed in modern cities. Researchers predict that the same mathematical models could be reformatted to estimate population size of ancient cities, as well as to develop measures for calculating socio-economic output like the production of art and public monuments based on the relationship size between settlement size and division of labor. Although there is still much to be solved through the equations of urban scaling theory, the consistency of city growth over time has implications for both the past and the present.
Citation: Ortman SG, Cabaniss AHF, Sturm JO, Bettencourt LMA (2014) The Pre-History of Urban Scaling. PLoS ONE 9(2): e87902. doi:10.1371/journal.pone.0087902
Image 2: doi:10.1371/journal.pone.0087902
Image 3: doi:10.1371/journal.pone.0087902
Image 4: doi:10.1371/journal.pone.0087902
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From the 9th to the mid-14th century, the region of Angkor in modern-day northern Cambodia was the capital of Khmer Empire and the largest preindustrial city in the world. Home to possibly more than three quarters of a million people, several different urban plans and reservoir systems, and impressive monuments like the temple of Angkor Wat (pictured from a bird’s-eye-view above), Angkor was the core of the Khmer Empire, which dominated Southeast Asia by the 11th century CE. Like many modern, booming cities, Angkor was fed by water sourced from another city.
Mahendraparvata, a hill-top site in the mountain range of Phnom Kulen, is significant as the birthplace of the Khmer Kingdom and as the seat of Angkor’s water supply. In 802 CE, Jayavarman II proclaimed himself the universal king of the Angkor region on the top Mahendraparvata. Jayavarma’s ascension to power marked the unification of the Angkor region and the foundation of the Khmer Empire.
Until recently, however, little was known about the urban settlement of Mahendraparvata; a dense forest canopy obscures a great deal of the area’s archaeological landscape. To determine the extent of land use around Mahendraparvata, the authors of a recent PLOS ONE paper examined soil core samples taken from one of the Phnom Kulen region’s reservoirs.
As Angkor’s source of water, Phnom Kulen’s archaeological landscape is littered with hydraulic structures, like dams, dykes, and reservoirs (points A, B, and E on the remote sensing digital image shown below), meant to store and direct Angkor’s water sources strategically. The researchers focused on an ancient reservoir upstream of the main river running north to south, now a swamp, to find evidence of intensive land use.
Core samples taken from the sediment of this ancient reservoir, point F on the image above, provided the researchers with chronological layers of earth containing organic materials, like wood, pollens, and spores, which could be assessed using radiocarbon dating.
By analyzing the sediment cores, researchers found that the reservoir was likely in use for about 400 years. Although the age of the reservoir itself remains inconclusive, sediment samples suggest that the valley was flooded in the mid-to-late 8th century CE, around the time Jayavarman II unified the area.
The authors found that medium-to-coarse sand deposition in the sediment samples beginning in the mid-9th century points to the presence of continual soil erosion, either from the surrounding hills or from the dyke itself, likely caused by deforestation in the area. By analyzing samples from the late 11th century, the authors found that the last and largest episode of erosion occurred, a possible result of intensive land use.
The researchers suggest that deforestation, as evidenced by soil erosion, implies that “settlement on Mahendraparvata was not only spatially extensive but temporally enduring.” In other words, the estimated extent of deforestation by continual sand deposits from the mid-9th century to the late-11th century in core samples indicates that Mahendraparvata was home to a large and thriving urban network in need of resources.
However, an increase in pollen spores dated to the 11th century, followed by the establishment of swamp forests in the early to mid-12th century in the reservoir, reflects that, by this time, the reservoir had fallen out of use, perhaps linked to changes in water management throughout the broader area, and possible population decline nearby. According to mid-16th century samples, the swamp flora around this time appears to have developed into the swamp flora seen today in the ruins of Mahendraparvata.
For some 400 years, the Phnom Kulen mountains acted as the main source of water for the Angkor region. The change of water management practices in the Phnom Kulen region has implications for the water supply to Angkor itself. In sum, by examining core samples drawn from one of Phnom Kulen’s ancient reservoirs, authors were able to explore an archaeological landscape that is still largely hidden and a history still mainly obscured by time. The potential link between the rise and fall of urban life in the Angkor region and the use of reservoirs the one used in this study helps to unearth a little bit more about the the Khmer Kingdom and the marked environmental impact of Mahendraparvata.
Citation: Penny D, Chevance J-B, Tang D, De Greef S (2014) The Environmental Impact of Cambodia’s Ancient City of Mahendraparvata (Phnom Kulen). PLoS ONE 9(1): e84252. doi:10.1371/journal.pone.0084252
Image 2: journal.pone.0084252
Image 3: journal.pone.0084252
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What does it take to topple a civilization, or a whole group of them? Over three thousand years ago, agriculture and trade-based societies flourished in the Eastern Mediterranean. Yet something fishy happened circa 1200 BC that brought these cultural and commercial centers to their knees—something that has left historians in the dark.
Correspondence from that time attributes the decline, at least partially, to invasions from a band of raiders, referred to as Sea Peoples. Other scholars studying this period point to natural disasters, such as earthquakes or drought. Research recently published in PLOS ONE reveals a more insidious culprit: Climate change may have fueled drought, the invasions, and eventually the collapse of these civilizations in what historians call the Late Bronze Age crisis.
To explore the environmental factors behind this crisis, the researchers took continuous core samples from modern-day Cyprus, at what is now called Larnaca Salt Lake, or Hala Sultan Tekke.
Core samples were analyzed for their pollen content and tested for the presence of dinoflagellates (pictured), a type of marine plankton. The researchers then studied the abundance and variety of plants represented by the ancient pollen and plotted fluctuations in the proportions of both between 1500 BC and 1500 AD. With similar data from nearby Syria, they reconstructed likely climate conditions in the region during the Late Bronze Age.
They found the abundance of marine plankton decreased around 1200 BC, suggesting the region was gradually becoming drier, as the lake lost its connection to the sea. The pollen record reveals a shift towards plants that could handle drier weather, indicating a decrease in rainfall. Dwindling rain, the researchers suggest, may have made it difficult to maintain agricultural production and led to food shortages. These shortages might also have caused people to travel, migrate, or raid in search of more food. This drought lasted three hundred years and coincides with the Sea People invasions.
It takes a lot to topple civilizations, and climate change has played its part in ending those in the Eastern Mediterranean during the Late Bronze Age. This evidence adds to the growing body of literature documenting the effects of climate change. This latest research adds a compelling chapter to the story of climate change, from which everyone can learn.
Citation: Kaniewski D, Van Campo E, Guiot J, Le Burel S, Otto T, et al. (2013) Environmental Roots of the Late Bronze Age Crisis. PLoS ONE 8(8): e71004. doi:10.1371/journal.pone.0071004
Keuninck (Coninck) Kerstiaen de – Fire of Troy, from Wikimedia
Thinking about spending the summer in the sun and sand? Early Neolithic humans may have thought so too, although with more survival-oriented goals in mind. A recent study published in PLOS ONE suggests that early humans, who set up camp in the Eastern Mediterranean (about 10,000 BCE), may have traveled as far as Saudi Arabia in search of game and water.
In this study, researchers unearthed several types of Neolithic arrowheads in the northern peninsula of Saudi Arabia at the site of Jebel Qattar, which suggests a link between Neolithic people of the Levant—modern-day Jordan, Lebanon, Syria, Israel, Palestine, and Cyprus—to areas as far south as Saudi Arabia. Arrowheads and other tools are, by and large, the main type of early human artifact observable today prior to the introduction of pottery (about 7000 BCE), and are integral to our understanding of the people who created and used them. Tools and arrowheads types, like the ones discovered at Jebel Qattar, provide researchers with evidence of early technology used for hunting.
Accurately identifying early Neolithic artifacts is a tough job—these arrowheads are over 10,000 years old, after all—and requires researchers to carefully sift out other objects uncovered during surface collection and trench excavations. In fact, the researchers discovered a total of 887 stone tools at the site of Jebel Qattar, only ten of which have been identified as Levantine types, known more specifically to researchers as El-Khiam and Helwan points. Named for their places of origin in Israel and Egypt respectively, the El-Khiam and Helwan arrowhead types are common to Levantine sites throughout the Neolithic period. This study, however, represents the first time archaeologists have discovered them in the Nefud Desert of Saudi Arabia.
Current understanding of early people living during the Neolithic period is rooted in excavation sites in the Levant and the larger area of the Fertile Crescent—the area in green on the map above—a geographical region containing parts of Western Asia, including the Levant, as well as parts of the Nile Valley and Nile Delta of northeast Africa. The Fertile Crescent is home to several major innovations, including the domestication of animals and the development of cereal, and is often known as the ‘cradle of civilization’. The discovery of El-Khiam and Helwan arrowheads in Saudi Arabia alludes to this hotspot of innovation and technology and suggests possible interaction between these early Neolithic peoples.
However, because so little evidence from the Neolithic period survives intact today, our understanding of Neolithic peoples is a work-in-progress. Nevertheless, tracing Neolithic people from the Levant as far as Saudi Arabia suggests that we may want to study broader areas when considering their trajectory. Of course, there is further exploration to be done beyond the borders of the Levant.
Citation: Crassard R, Petraglia MD, Parker AG, Parton A, Roberts RG, Jacobs Z, Alsharekh A, Al-Omari A, Breeze P, Drake NA, Groucutt HS, Jennings R, Re´gagnon E, and Shipton C . (2013) Beyond the Levant: First Evidence of a Pre-Pottery Neolithic Incursion into the Nefud Desert, Saudi Arabia. PLOS ONE 8(7): e68061. doi: 10.1371/journal.pone.0068061
Images: doi: 10.1371/journal.pone.0068061
While the tale of how man’s best friend came to be (i.e., domestication) is still slowly unfolding, a recently published study in PLOS ONE may provide a little context—or justification?—for dog lovers everywhere. It turns out that even thousands of years ago, humans loved to share food with, play with, and dress up their furry friends.
In the study titled “Burying Dogs in Ancient Cis-Baikal, Siberia: Temporal Trends and Relationships with Human Diet and Subsistence Practices,” biologists, anthropologists, and archaeologists joined forces to investigate the nature of the ancient human-dog relationship by analyzing previously excavated canid remains worldwide, with a large portion of specimens in modern-day Eastern Siberia, Russia. The authors performed genetic analysis and skull comparisons to establish that the canid specimens were most likely dogs, not wolves, which was an unsurprising but important distinction when investigating the human-canine bond. The canid skulls from the Cis-Baikal region most closely resembled large Siberian huskies, or sled dogs. Radiocarbon dating from previous studies also provided information regarding the dates of death and other contextual information at the burial sites.
The researchers found that the dogs buried in Siberia, many during the Early Neolithic period 7,000-8,000 years ago, were only found at burial sites shared with foraging humans. Dogs were found buried in resting positions, or immediately next to humans at these sites, and their graves often included various items or tools seemingly meant for the dogs. One dog in particular was adorned with a red deer tooth necklace around its neck and deer remnants by its side, and another was buried with what appears to be a pebble or toy in its mouth.
By analyzing the carbon and nitrogen in human and dog specimens in this region, the researchers were able to determine similarities in human and dog diets, both of which were rich in fish. This finding may be somewhat surprising because one might assume that dogs helped humans hunt terrestrial game, and would consequently be less likely found among humans that ate primarily fish.
The authors speculate that dogs were considered spiritually similar to humans, and were therefore buried at the same time in the same graves. The nature of the burials and the similarities in diet also point toward an intimate and personal relationship, both emotional and social, between humans and their dogs—one that involved sharing food and giving dogs the same burial rites as the humans they lived among. Ancient dogs weren’t just work animals or hunters, the authors suggest, but important companion animals and friends as well.
Citation: Losey RJ, Garvie-Lok S, Leonard JA, Katzenberg MA, Germonpré M, et al. (2013) Burying Dogs in Ancient Cis-Baikal, Siberia: Temporal Trends and Relationships with Human Diet and Subsistence Practices. PLoS ONE 8(5): e63740. doi:10.1371/journal.pone.0063740
Image Credits: Losey RJ, Garvie-Lok S, Leonard JA, Katzenberg MA, Germonpré M, et al. (2013) Burying Dogs in Ancient Cis-Baikal, Siberia: Temporal Trends and Relationships with Human Diet and Subsistence Practices. PLoS ONE 8(5): e63740. doi:10.1371/journal.pone.0063740
Siberian husky photo by Pixel Spit