Monday, August 22, 2016

Human sacrifice at the Sanctuary of Zeus?

Important new discoveries have recently come to light at the Sanctuary of Zeus at Mt. Lykaion, located high in the Arcadian mountains of Greece, and known in antiquity as the birthplace of Zeus. The southern peak of the mountain served as a primitive ash altar for burnt animal sacrifices to Zeus, and the lower mountain meadow hosted famous athletic festivals.

Since 2004, a Greek-American archaeological team, the Mt. Lykaion Excavation and Survey Project, has been working at the sanctuary, and excavations at the altar have proven to be very rich and informative. Significant recent discoveries include pottery as early as the Neolithic, Early Helladic and Middle Helladic periods, and the presence of a significant Mycenaean mountain top shrine as well as an Early Iron Age cult place. There is abundant evidence for animal sacrifice, predominantly from goat and sheep femurs, representing continuous cult activity from the Mycenaean period through to the Hellenistic period. It is likely that Zeus was worshipped here from the 16 th century B.C., in the early Mycenaean period.

During the summer of 2016 from a trench located near the center of the mountain top, and close to a man-made platform of stones, a human burial was found in the sacrificial altar, within a simple border of field stones on the long sides, and with an east-west orientation. The length of the stones is 1.52 meters. The central portion of the burial was covered with stone slabs over the pelvis area. Several ancient literary sources mention rumors that human sacrifice took place at the altar, but up until a few weeks ago there has been no trace whatsoever of human bones discovered at the site. Preliminary analysis suggests that the skeleton was that of an adolescent, and the ceramic evidence found with the body suggests that the burial was made during the eleventh century B.C., after the collapse of the Mycenaean palaces at the time of transition from the end of the Late Bronze Age to the Early Iron Age. Scientific analyses of the bones will be undertaken immediately, and although it is premature to speculate on the nature of the death of the individual, the prominent location of the burial within the sacrificial altar, and its east-west orientation, indicate its significance.

New discoveries were also made in the lower mountain meadow, site of the lower sanctuary. Some of the highlights include an impressive stone staircase at the top of the 4 th century B.C. corridor, and a large stone archway at the other end, presumably through which athletes would have descended towards the hippodrome and stadium. In the Administrative Building, a large, decorated terracotta sima block was uncovered. In a large circular depression, visible from Google Earth, to the west of the Stoa, and to the east of the fountain house, excavations revealed two well preserved water channels, a stone water basin, and the beginning of a stone wall, perhaps to be associated with the Sanctuary of Pan. Within the hippodrome, the only visible example in the Greek world, the racecourse floor was exposed. Work in the area of the 4 th century bath facility has revealed walls from earlier levels. The present work will continue at the sanctuary until 2020.
FIG. 2 Human burial found near the center of the ash altar of Zeus with stones covering the central portion of the body.
FIG. 3 Human burial with stones removed.
FIG. 4 Detail of head and chest of body.
FIG. 5 Early 11 th century B.C. bowl fragment found with the skeleton.
FIG. 6 Overall view of the Lower Sanctuary including administrative building, stoa, hippodrome, stadium and bath.
FIG. 7 Plan of the Sanctuary of Zeus at Mt. Lykaion.
FIG. 8 Map of the Peloponnesos showing the location of Mt. Lykaion
FIG. 9 Corridor with stone staircase

Wednesday, August 10, 2016

Textbook story of how humans populated America is 'biologically unviable,' study finds

Map outlining the opening of the human migration routes in North America revealed by the results presented in this study.
Mikkel Winther Pedersen

Established theory about the route by which Ice Age peoples first reached the present-day United States has been challenged by an unprecedented study which concludes that their supposed entry route was "biologically unviable".

The first people to reach the Americas crossed via an ancient land bridge between Siberia and Alaska but then, according to conventional wisdom, had to wait until two huge ice sheets that covered what is now Canada started to recede, creating the so-called "ice-free corridor" which enabled them to move south.

In a new study published in the journal Nature, however, an international team of researchers used ancient DNA extracted from a crucial pinch-point within this corridor to investigate how its ecosystem evolved as the glaciers began to retreat. They created a comprehensive picture showing how and when different flora and fauna emerged and the once ice-covered landscape became a viable passageway. No prehistoric reconstruction project like it has ever been attempted before.

The researchers conclude that while people may well have travelled this corridor after about 12,600 years ago, it would have been impassable earlier than that, as the corridor lacked crucial resources, such as wood for fuel and tools, and game animals which were essential to the hunter-gatherer lifestyle.

If this is true, then it means that the first Americans, who were present south of the ice sheets long before 12,600 years ago, must have made the journey south by another route. The study's authors suggest that they probably migrated along the Pacific coast.

Who these people were is still widely disputed. Archaeologists agree, however, that early inhabitants of the modern-day contiguous United States included the so-called "Clovis" culture, which first appear in the archaeological record over 13,000 years ago. And the new study argues that the ice-free corridor would have been completely impassable at that time.

The research was led by Professor Eske Willerslev, an evolutionary geneticist from Centre for GeoGenetics, University of Copenhagen and University of Cambridge, who also hold posts at St John's College and the Wellcome Sanger Institute.

"The bottom line is that even though the physical corridor was open by 13,000 years ago, it was several hundred years before it was possible to use it," Willerslev said.

"That means that the first people entering what is now the US, Central and South America must have taken a different route. Whether you believe these people were Clovis, or someone else, they simply could not have come through the corridor, as long claimed."

Mikkel Winther Pedersen, a PhD student at the Centre for GeoGenetics, University of Copenhagen, who conducted the molecular analysis, added: "The ice-free corridor was long considered the principal entry route for the first Americans. Our results reveal that it simply opened up too late for that to have been possible."

The corridor is thought to have been about 1,500 kilometres long, and emerged east of the Rocky Mountains 13,000 years ago in present-day western Canada, as two great ice sheets - the Cordilleran and Laurentide, retreated.

On paper, this fits well with the argument that Clovis people were the first to disperse across the Americas. The first evidence for this culture, which is named after distinctive stone tools found near Clovis, New Mexico, also dates from roughly the same time, although many archaeologists now believe that other people arrived earlier.

"What nobody has looked at is when the corridor became biologically viable," Willerslev said. "When could they actually have survived the long and difficult journey through it?"

The conclusion reached by Willerslev and his colleagues is that the journey would have been impossible until about 12,600 years ago. Their research focused on a "bottleneck", one of the last parts of the corridor to become ice-free, and now partly covered by Charlie Lake in British Columbia, and Spring Lake, Alberta - both part of Canada's Peace River drainage basin.

The team gathered evidence including radiocarbon dates, pollen, macrofossils and DNA taken from lake sediment cores, which they obtained standing on the frozen lake surface during the winter season. Willerslev's own PhD, 13 years ago, demonstrated that it is possible to extract ancient plant and mammalian DNA from sediments, as it contains preserved molecular fossils from substances such as tissue, urine, and faeces.

Having acquired the DNA, the group then applied a technique termed "shotgun sequencing". "Instead of looking for specific pieces of DNA from individual species, we basically sequenced everything in there, from bacteria to animals," Willerslev said. "It's amazing what you can get out of this. We found evidence of fish, eagles, mammals and plants. It shows how effective this approach can be to reconstruct past environments."

This approach allowed the team to see, with remarkable precision, how the bottleneck's ecosystem developed. Crucially, it showed that before about 12,600 years ago, there were no plants, nor animals, in the corridor, meaning that humans passing through it would not have had resources vital to survive.

Around 12,600 years ago, steppe vegetation started to appear, followed quickly by animals such as bison, woolly mammoth, jackrabbits and voles. Importantly 11,500 years ago, the researchers identified a transition to a "parkland ecosystem" - a landscape densely populated by trees, as well as moose, elk and bald-headed eagles, which would have offered crucial resources for migrating humans.

Somewhere in between, the lakes in the area were populated by fish, including several identifiable species such as pike and perch. Finally, about 10,000 years ago, the area transitioned again, this time into boreal forest, characterised by spruce and pine.

The fact that Clovis was clearly present south of the corridor before 12,600 years ago means that they could not have travelled through it. David Meltzer, an archaeologist at Southern Methodist University and a co-author on the study, said: "There is compelling evidence that Clovis was preceded by an earlier and possibly separate population, but either way, the first people to reach the Americas in Ice Age times would have found the corridor itself impassable."

"Most likely, you would say that the evidence points to their having travelled down the Pacific Coast," Willerslev added. "That now seems the most likely scenario."

Sensational grave find in Cypriote Bronze Age city

This is a Mycenaean (Greek) vessel with fish motifs, c. 1300 BC.
Peter Fischer

An archaeological expedition from the University of Gothenburg has discovered one of the richest graves from the Late Bronze Age ever found on the island of Cyprus. The grave and its offering pit, located adjacent the Bronze Age city of Hala Sultan Tekke, contained many fantastic gold objects such as a diadem, pearls, earrings and Egyptian scarabs, as well as more than 100 richly ornamented ceramic vessels. The objects, which originate from several adjacent cultures, confirm the central role of Cyprus in long-distance trade.

Hala Sultan Tekke, a Bronze Age city from 1600-1150 BC that covered an area of up to 50 hectares, had far-reaching trade connections that included Sweden. Peter Fischer, professor of Cypriote archaeology at the University of Gothenburg, has led the excavations performed by the Swedish Cyprus expedition for seven seasons since 2010.

'The excavations in May and June this year were the most successful to date. We discovered an older city quarter from around 1250 BC and outside the city we found an incredibly rich grave, one of the richest in Cyprus from this period, and an offering pit next to it. The fact that we have discovered a burial site from the Late Bronze Age is quite sensational, since those who died around this time were usually buried within the settlement,' says Fischer.

The area where the grave was found is exposed to erosion caused by farming. Prior to the excavation, a so-called geophysical survey was performed using radar equipment able to identify what is in the ground down to a depth of two metres. The surveying revealed almost 100 underground 'pits', some of which turned out to be wells, some offering pits and - as this year - a grave.

'Wells are usually one metre in diameter, but this structure was 4 x 3 metres. The grave seems to be a family tomb for eight children ages 5-10 years and nine adults, of whom the oldest was about 40 years old. The life expectancy was much shorter back then than it is today,' says Fischer.

The archaeologists found over 100 ceramic vessels and several gold finds, including a diadem, beads, earrings and Egyptian scarabs (picture 1), in the grave and the offering pit. The finds also include gemstones and five cylinder seals, some produced locally and some from Syria and Mesopotamia, as well as a bronze dagger.

The archaeologists assign the greatest importance to the more than 140 complete ceramic vessels, most of which were decorated with spectacular illustrations of for example people sitting in a chariot drawn by two horses and a woman wearing a beautiful dress (picture 2). There were also vases decorated with religious symbols and animal illustrations of for example fish. Many of the vessels were imported mainly from Greece and Crete but also from Anatolia, or the equivalence of present-day Turkey.

'The pottery carries a lot of archaeological information. There were for example high-class Mycenaean imports, meaning pottery from Greece, dated to 1500-1300 BC. The motif of the woman, possibly a goddess, is Minoan, which means it is from Crete, but the vase was manufactured in Greece. Back in those days, Crete was becoming a Greek "colony",' says Fischer.

According to Fischer, the painting of the woman's dress is highly advanced and shows how wealthy women dressed around this time. The motif can also be found on frescos for example in the Palace of Knossos in Heraklion, Crete. Other finds are from Egypt. Two of the stone scarabs are gold-mounted and one features hieroglyphs spelling 'men-kheper-re' next to an illustration of a pharaoh. This has given the archaeologists a unique opportunity to tie the roughly 3,500-year-old find to a historic person. The inscription refers to Egypt's most powerful pharaoh Thutmose III (1479-1425 BC), during whose reign Egypt peaked in size and influence as he conquered both Syria and parts of Mesopotamia, present-day Iraq.

'We also found evidence in the city of large-scale manufacturing and purple-dying of textiles. These products were used in the trade with the high cultures in Egypt, Anatolia, the Levant, Mesopotamia, Crete and Greece, which explains the rich imported finds.

What is most interesting about the finds is the dating: they are from 1500/1400 BC, but the researchers have still only found the burial site but not the city from this period.

'It must have been a rich city judging from the grave we found this year. But it is most likely located closer to the burial site in an area that still has not been explored,' says Fischer.

This year's excavation period is over and until next year's on-site work begins, the researchers have some intense processing of finds to look forward to.

'In spring 2017 we'll continue our uncovering of parts of the city and the burial site. As the integrity of both areas is threatened by agricultural activities, there is a need for quick action to secure our shared cultural heritage before it is destroyed forever,' says Fischer.

Tuesday, August 9, 2016

Gaited horses most likely originated in the 9th century medieval England

Some horses have special gaits, which are more comfortable for the rider than walk, trot or gallop. Now, a study by an international research team under the direction of the Leibniz Institute for Zoo and Wildlife Research (IZW) in Berlin revealed that these gaited horses most likely originated in the 9th century medieval England. From there they were brought to Iceland by the Vikings and later spread all over Europe and Asia. These findings were published in the current issue of the journal "Current Biology."

Walk, trot and gallop are the gaits which all horses can master. However, riders who want to sit in their saddle more comfortably while still making good time on long journeys would benefit from choosing gaited horses. They are able to perform special gaits, like the ambling or pacing, which are typical for Icelandic horses and allow for a smoother ride. Responsible for this ability is a mutation in the DMRT3 gene, which was recently shown by a study with over 4,000 horses from different breeds. To investigate the history of gaited horses the scientist analysed this mutation in the genome of 90 horses from the Copper Age (6000 BC) to the Middle Ages (11th century). They detected the mutation in samples of two English horses from 850 -- 900 AD and more frequently in Icelandic horses dating to the 9th -- 11th century. Most likely the first gaited horses appeared in medieval England and were then transported to Iceland by the Vikings. Horses have existed in Iceland since 870 BC. In contrast, no European (Scandinavia included) or Asian horse of the same period carrying the mutation for the alternative gaits was found.

It is improbable that the English and Icelandic gaited horse populations developed independently from each other in such a short time. "It is much more likely, that the first horses ever imported to Iceland already carried the mutation for alternative gaits. The Vikings recognised the value of the gaited horses and preferentially selected for this trait -- thereby laying the foundation for the worldwide distribution," explains Arne Ludwig, geneticist at the IZW. 

Historic sagas also suggest that Icelandic horses exhibited the ability for alternative gaits at a very early stage. Although the origin of the Icelandic horse is not fully resolved, the general assumption is that they came to the island together with the Vikings. However, since the mutation was not found in Scandinavian horses of the 9th century, horses from other regions must have been brought to Iceland as well.

Historic records report that Vikings were repeatedly pillaging on the British Isles and conquered the region of today's Yorkshire -- precisely the region the two historic gaited horses originated from. "Taking that into account our results suggest that Vikings first encountered gaited horses on the British Isles and transported them to Iceland," explains Saskia Wutke, PhD student at the IZW and first lead author of the study. The high frequency of the mutation for gaitedness in the early Icelandic horses indicates that the Icelandic settlers preferably bred gaited horses -- apparently the comfortable gaits proved to be particularly suitable for long distance travel through rough terrain.

Monday, August 8, 2016

Fresh look at burials, mass graves, tells a new story of Cahokia

A new study challenges earlier interpretations of an important burial mound at Cahokia, a pre-Columbian city in Illinois near present-day St. Louis. The study reveals that a central feature of the mound, a plot known as the "beaded burial," is not a monument to male power, as was previously thought, but includes both males and females of high status.

The new study, published in the journal American Antiquity, is one of several recent analyses of the site from researchers at the Illinois State Archaeological Survey at the University of Illinois and their colleagues at other institutions. All of the studies confirm the presence of males and females in the beaded burial.

In 1967, archaeologist Melvin Fowler discovered a massive burial site at Cahokia while excavating an unusual, ridgetop mound. This mound, now called Mound 72, held five mass graves, each containing 20 to more than 50 bodies, with dozens of other bodies buried individually or in groups, sometimes directly over the mass graves. Fowler identified 270 bodies in the mound.

Beaded burial at Cahokia.
Graphic: Julie Mahon

Scientists later determined that all of the burials occurred between about 1000 and 1200, during the rise and peak of Cahokia's power and influence. Some of the burials appeared to be high-status individuals whose bodies were placed on cedar litters.

"Mound 72 burials are some of the most significant burials ever excavated in North America from this time period," said ISAS director Thomas Emerson, who conducted the most recent study with physical anthropologist Kristin Hedman and skeletal analysts Eve Hargrave of ISAS, Dawn Cobb of the Illinois State Museum Society, and Andrew Thompson of the University of Cincinnati College of Medicine. The ISAS is a division of the Prairie Research Institute at Illinois.

"Fowler's and others' interpretation of these mounds became the model that everybody across the east was looking at in terms of understanding status and gender roles and symbolism among Native American groups in this time," Emerson said.

Emerson and his colleagues discovered that some of those early interpretations were based on inaccurate and incomplete information. Most of the errors involved the beaded burial. Here, two central bodies were placed, one on top of the other, on a partial bed of beads that also ran between and around the bodies. Several other bodies, buried at the same time, were arranged around this pair.

Fowler and later archaeologists came to believe that this was a burial of two high-status males surrounded by their servants. They interpreted the arrangement of beads associated with these central figures as the remains of a beaded cape or blanket in the shape of a bird. The pattern of beads near the heads of the two central bodies resembled a bird head, some thought.

Because the bird is a common motif related to warriors and supernatural beings in some Native American traditions, Fowler proposed that the central males of the beaded burial represented mythical warrior chiefs.

"One of the things that promoted the concept of the male warrior mythology was the bird image," Emerson said. Once this interpretation took hold, many researchers came to see this as evidence that Cahokia was "a male-dominated hierarchy," he said.

A fresh look at the early archaeologists' maps, notes and reports and the skeletal remains told a new and surprising story. First, the researchers found that there were 12 bodies associated with the beaded burial - not six, as had been previously reported. And independent skeletal analyses conducted by each of the co-authors - Thompson, Hedman, Hargrave and Cobb - revealed that the two central bodies in the beaded burial were actually male and female.

Further analyses revealed other male-female pairs on top of, and near, the beaded area. Some were laid out as fully articulated bodies. Others were disarticulated bodies, the bones of which had been gathered and bundled for burial near these important couples. The researchers also discovered the remains of a child.

"We had been checking to make sure that the individuals we were looking at matched how they had been described," Hedman said. "And in re-examining the beaded burial, we discovered that the central burial included females. This was unexpected."

"The fact that these high-status burials included women changes the meaning of the beaded burial feature," Emerson said. "Now, we realize, we don't have a system in which males are these dominant figures and females are playing bit parts. And so, what we have at Cahokia is very much a nobility. It's not a male nobility. It's males and females, and their relationships are very important."

The new findings are more in line with other evidence from Cahokia, Emerson said.

"For me, having dug temples at Cahokia and analyzed a lot of that material, the symbolism is all about life renewal, fertility, agriculture," he said. "Most of the stone figurines found there are female. The symbols showing up on the pots have to do with water and the underworld. And so now Mound 72 fits into a more consistent story with what we know about the rest of the symbolism and religion at Cahokia."

Emerson said that those who saw warrior symbolism at Cahokia missed the special culture of the time period.

"When the Spanish and the French came into the southeast as early as the 1500s, they identified these kinds of societies in which both males and females have rank," he said. "Really, the division here is not gender; it's class."

"People who saw the warrior symbolism in the beaded burial were actually looking at societies hundreds of years later in the southeast, where warrior symbolism dominated, and projecting it back to Cahokia and saying: 'Well, that's what this must be,'" Emerson said. "And we're saying: 'No, it's not.'"

Other recent findings related to the people buried in Mound 72 are described in the Journal of Archaeological Science, the American Journal of Physical Anthropology, and a chapter in the book "Beyond Collapse: Archaeological Perspectives on Resilience, Revitalization and Transformation in Complex Societies."


Residual remains of butchered animals on stone tools used 250,000 years ago in Jordan

How smart were human-like species of the Stone Age? New research published in the Journal of Archaeological Science by a team led by paleoanthropologist April Nowell of the University of Victoria reveals surprisingly sophisticated adaptations by early humans living 250,000 years ago in a former oasis near Azraq, Jordan.

The research team from UVic and partner universities in the US and Jordan has found the oldest evidence of protein residue -- the residual remains of butchered animals including horse, rhinoceros, wild cattle and duck -- on stone tools. The discovery draws startling conclusions about how these early humans subsisted in a very demanding habitat, thousands of years before Homo sapiens first evolved in Africa.

The team excavated 10,000 stone tools over three years from what is now a desert in the northwest of Jordan, but was once a wetland that became increasingly arid habitat 250,000 years ago. The team closely examined 7,000 of these tools, including scrapers, flakes, projectile points and hand axes (commonly known as the "Swiss army knife" of the Paleolithic period), with 44 subsequently selected as candidates for testing. Of this sample, 17 tools tested positive for protein residue, i.e. blood and other animal products.

"Researchers have known for decades about carnivorous behaviours by tool-making hominins dating back 2.5 million years, but now, for the first time, we have direct evidence of exploitation by our Stone Age ancestors of specific animals for subsistence," says Nowell. "The hominins in this region were clearly adaptable and capable of taking advantage of a wide range of available prey, from rhinoceros to ducks, in an extremely challenging environment."

"What this tells us about their lives and complex strategies for survival, such as the highly variable techniques for prey exploitation, as well as predator avoidance and protection of carcasses for food, significantly diverges from what we might expect from this extinct species," continues Nowell. "It opens up our ability to ask questions about how Middle Pleistocene hominins lived in this region and it might be a key to understanding the nature of interbreeding and population dispersals across Eurasia with modern humans and archaic populations such as Neanderthals."

Another result of this study is the potential to revolutionize what researchers know about early hominin diets. "Other researchers with tools as old or older than these tools from sites in a variety of different environmental settings may also have success when applying the same technique to their tools, especially in the absence of animal remains at those sites," adds Nowell.

Wednesday, August 3, 2016

Why people in eastern North America domesticated plants for the first time about 5,000 years ago

This map shows the area covered by a new University of Utah study that concludes a population boom and resulting scarcity of wild foods are what caused early people in eastern North America to domesticate wild food plants for the first time on the continent starting about 5,000 year ago. The triangles and names represent archaeological sites previously identified as locations where one or more of the these plants first were domesticated: squash, sunflower, marshelder and pitseed goosefoot, a relative of quinoa. The small circles are sites where radiocarbon-dated artifacts have been found, with a single circle often representing many dated artifacts. The study area includes much of eastern North America inland from the Atlantic and Gulf coasts. 
Credit: Elic Weitzel, University of Utah
University of Utah anthropologists counted the number of carbon-dated artifacts at archaeological sites and concluded that a population boom and scarce food explain why people in eastern North America domesticated plants for the first time on the continent about 5,000 years ago.

"Domesticated plants and animals are part of our everyday lives, so much so that we take them for granted," says Brian Codding, senior author of the study published online August 2 by the British journal Royal Society Open Science. "But they represent a very unique thing in human history. They allowed for large numbers of people to live in one place. That ultimately set the stage for the emergence of civilization."

Graduate student Elic Weitzel, the study's first author, adds: "For most of human history, people lived off wild foods -- whatever they could hunt or gather. It's only relatively recently that people made this switch to a very different method of acquiring their food. It's important to understand why that transition happened."

The study dealt not with a full-fledged agricultural economy, but with the earlier step of domestication, when early people in eastern North America first started growing plants they had harvested in the wild, namely, squash, sunflower, marshelder and a chenopod named pitseed goosefoot, a pseudocereal grain closely related to quinoa.

Codding, an assistant professor of anthropology, says at least 11 plant domestication events have been identified in world history, starting with wheat about 11,500 years ago in the Middle East. The eastern North American plant domestication event, which began around 5,000 years ago, was the ninth of those 11 events and came after a population boom 6,900 to 5,200 years ago, he adds.

For many years, two competing theories have sought to explain the cause of plant domestication in eastern North America: First, population growth and resulting food scarcity prompted people to grow foods on which they already foraged. Second, a theory called "niche construction" or "ecosystem engineering" that basically says intentional experimentation and management during times of plenty -- and not immediate necessity -- led people to manage and manipulate wild plants to increase their food supply.

"We argue that human populations significantly increased prior to plant domestication in eastern North America, suggesting that people are driven to domestication when populations outstrip the supply of wild foods," Weitzel says.

"The transition to domesticating food allowed human populations to increase drastically around the world and made our modern way of life possible," he adds. "People start living near the fields. Whenever you've got sedentary communities, they start to expand. Villages expand into cities. Once you have that, you have all sorts of social changes. We really don't see state-level society until domestication occurs."

When early North Americans first domesticated crops

The region of eastern North America covered by the study includes most of Missouri, Illinois, Indiana, Ohio, West Virginia, Kentucky, Tennessee and Arkansas, and portions of Oklahoma, Kansas, Iowa, Virginia, North Carolina, South Carolina, Georgia, Mississippi and Louisiana.

"This is the region where these plant foods were domesticated from their wild variants," Weitzel says. "Everywhere else in North America, crops were imported from elsewhere," particularly Mexico and Central America.

Four indigenous plant species constitute what scientists call the Eastern Agricultural Complex, which people began to domesticate about 5,000 years ago.

Previous research shows specific domestication dates were 5,025 years ago for squash at an archaeological site named Phillips Spring in Missouri, 4,840 years ago for sunflower seeds domesticated at Hayes in Tennessee, 4,400 years ago for marshelder at the Napoleon Hollow site in Illinois, and 3,800 years ago for pitseed goosefoot found in large quantities at Riverton, Illinois, along with squash, sunflower and marshelder.

Three more recent sites also have been found to contain evidence of domestication of all four species: Kentucky's Cloudsplitter and Newt Kindigenash rockshelters, dated to 3,700 and 3,640 years ago, respectively, and the 3,400-year-old Marble Bluff site in Arkansas.

Sunflower and squash -- including acorn and green and yellow summer squashes -- remain important crops today, while marshelder and pitseed goosefoot are not (although the related quinoa is popular).

Deducing population swings from radiocarbon dates

"It's really difficult to arrive at measures of prehistoric populations. So archaeologists have struggled for a long time coming up with some way of quantifying population levels when we don't have historical records," Weitzel says.

"People have looked at the number of sites through time, the number of artifacts through time and some of the best work has looked at the effects of population growth," such as in the switch from a diet of tortoises to rabbits as population grew in the eastern Mediterranean during the past 50,000 years, he adds.

Codding says that in the past decade, archaeologists have expanded the use of radiocarbon-dates for artifacts to reconstruct prehistoric population histories. Weitzel says radiocarbon dates in the new study came from artifacts such as charcoal, nutshells and animal bones -- all recorded in a database maintained by Canadian scientists.

The University of Utah anthropologists used these "summed radiocarbon dates" for 3,750 dated artifacts from eastern North America during the past 15,000 years.

"The assumption is that if you had more people, they left more stuff around that could be dated," Weitzel says. "So if you have more people, you conceivably should have more radiocarbon dates."
"We plotted the dates through time," namely, the number of radiocarbon dates from artifacts in every 100-year period for the past 15,000 years, he adds.

The analysis indicated six periods of significant population increase or decrease during that time, including one during which population nearly doubled in eastern North America starting about 6,900 years ago and continuing apace until 5,200 years ago -- not long before plant domestication began, Codding says.

Codding notes that even though plant domestication meant "these people were producing food to feed themselves and their families, they're still hunting and foraging," eating turtles, fish, water fowl and deer, among other animals.

The other theory

Weitzel says the concept of niche construction is that people were harvesting wild plants, and "were able to get more food from certain plants." By manipulating the environment -- such as transplanting wild plants or setting fires to create areas favorable for growth of wild food plants -- they began "experimenting with these plants to see if they could grow them to be bigger or easier to collect and consume," he adds. "That kind of experimentation then leads to domestication."

Codding says: "The idea is that when times are good and people have plenty of food then they will experiment with plants. We say that doesn't provide an explanation for plant domestication in eastern North America." He believes the behavioral ecology explanation: increasing population and-or decreasing wild food resources led to plant domestication.