Tag Archives: Clovis culture

Humans may have first arrived in North America as early as 30,000 years ago

Stone tool found below the Last Glacial Maximum (LGM) layer at Chiquihuite Cave. Credit: Ciprian Ardelean.

Until not too long ago, the consensus among archaeologists and anthropologists used to be  that the first humans arrived in the Americas by crossing a narrow land bridge between Siberia and glacier-covered Alaska some 14,000 years ago towards the end of the Last Glacial Period. However, research carried out over the past 15 years suggests that the timeline of human settlement in the Americas stretches further back in time than previously believed.

Two new studies published this week suggest that the first humans set foot in the lower 48 states as early as 30,000 years ago, drawing from extensive fieldwork across dozens of archaeological sites in North and Central America.

What’s more, this newly refined timeline of human dispersal also casts doubt over the accepted migratory path. Rather than entering North America from Asia via Beringia (the now-submerged land bridge between Eurasia and Alaska), the new findings point towards a route along the Pacific Coast as a more likely entry and dispersal point.

The human journey into the Americas may have first begun at least 10,000 years earlier than previously thought

Assistant professor Mikkel Winther Pedersen with team members carefully sampling the different cultural layers in the cave. Credits: Mads Thomsen.

There is still much uncertainty regarding the timeline of the migration and the divergence between the northern and southern Amerindian populations.

The first natives to the Americas were widely believed to be the Clovis, named so after the town of Clovis, New Mexico, where archeologists found “matted masses of mammoth bones” and slender, finger-long spear points during the 1930s. These weapons — known as Clovis points due to their characteristic flaking technique — have been found across more than 1,500 sites in the southeast and central contiguous United States, dating as far back as 13,000-14,000 years ago.

However, growing archaeological and genetic evidence since the early 2000s disputes the notion that the Americas were originally populated by Clovis people. Instead, there were likely multiple migrations of people from Asia.

Ciprian Ardelean, a researcher and lecturer at the Universidad Autónoma de Zacatecas, and colleagues performed excavations at a cave in Zacatecas, in central Mexico. They found a treasure trove of stone tool artifacts, as well as plant remains. Dating suggests that some of the flaked stone tools cover a long occupation ranging from 31,000 years ago to 12,500 years ago, predating the Clovis culture by many thousands of years.

“The peopling of America is the ultimate battlefield in American archaeology and one of the last legitimate mysteries in world archaeology. I became obsessed with these questions over the years. Doing Mayan archaeology for several years (1999-2006) showed me that there were few true mysteries left to address in Mayan culture, that most discoveries were basically repetitions of already known finds so that was not challenging enough. Ice Age archaeology, instead, is full of real enigmas and there are new questions surging over and over again, constantly. That attracted me to the point that I completely changed the direction of my professional life,” Ardelean told ZME Science.

Ardelean has been investigating hunter-gatherer sites in the region since 2009, while he was still a Ph.D. candidate. Previously, the archaeological sites he had access to were too recent for his interests, spanning only the last 1,500 years. They were also too extremely eroded for any meaningful work. This is why he focused his attention on caves, which can preserve remains and artifacts better. Caves are also excellent natural shelters that would have been extremely appealing to early humans.

“Following information from local villagers, one colleague and I visited Chiquihuite Cave for the first time in May 2010. The first test excavation was done in 2012 for my PhD thesis. I managed to find a few stone flakes in a layer that was dated to almost 30,000 years ago. That was sufficient motivation to search for funding and grants and start excavations on a larger scale,” said Ardelean.

With funding secured, Ardelean returned to Chiquihuite Cave between 2015 and 2017, where he began major excavations — but also had to face innumerable challenges that come with the territory of conducting fieldwork in an area constantly besieged by “drug wars and profound instability”.

To reach the high-altitude cave, perched more than 1,000 meters above the closest village, the archeologists had to drive 4×4 trucks up the mountain, before continuing the rest of their journey up the steep slopes to the site on the back of donkeys and mules. Over 40 pack animals and 40 people, including local villagers, formed huge caravans carrying equipment and retrieved artifacts during each excavation season.

“We lived inside the cave, for 7 weeks in a row each time, without leaving it. All the food, water, gasoline (for power plants) was carried from the beginning of the season, calculated to last for 7 weeks. We camped inside the cave and cooked at the entrance of the cave. We never took showers or bathed during the field season; only minor intimate hygiene was possible. We always worked during winters, at 2740 m of altitude. In summers, it’s wet and stormy, one cannot work up there; it has to be winter, which is the dry season here. Sometimes, we had snow, hail, cold rain and strong winds; sometimes, the temperature outside dropped to -10ºC. But, inside the cave, the temperature always stays still at +12ºC, day and night. This makes the cave a potential perfect shelter for spending winters during the harsh Last Glacial Maximum (LGM) conditions,” said Ardelean.

“The excavation was done far inside the cave, at 50 m away from the entrance. The ancient entrance was buried under tonnes of rocks fallen from the cliffs around 12,000 years ago, blocking the access. It is possible to excavate along the ancient entrance (drip line), which also prevents us from discovering many important things, such as the fireplaces and diet remains. So far inside the cave, it’s difficult to hope for something other than stone tools and debitage.”

This particular piece was made from a greenish crystallized limestone. Credit: Ciprian Ardelean.

The fieldwork, which was described in a study published in Naturetoday, indicate that the cave was constantly occupied by ancient human groups over a period of nearly 20,000 years.

This timeline runs counter to the currently established narrative among scholars. Although the paradigm of the earliest human dispersal in the Americas has shifted towards a pre-Clovis presence, the threshold is set to around 18,000 years ago.

Although earlier artifacts than this threshold have been reported in the scientific literature in the past, the establishment is reluctant to accept earlier timelines. According to Ardelean, it is widely believed that the climatic conditions at the end of the Last Glacial Maximum (LGM) would have made it impossible for hunter-gatherers to cross Asia into Alaska due to massive ice caps that occupied the entire territory of Canada from coast to coast.

“The finds will be considered controversial and I will obviously receive many attacks and rejections. That is normal in American prehistory, which is highly paradigmatic and reticent to challenges,” Ardelean said.

“In my case, the discovery is based almost exclusively on flaked stone tools. Unfortunately, until now, we have not found undeniable modified bone or other sort of indicators. However, the tools are human-made, beyond any doubt. I have spent years with them in my hands, in successive rounds of analysis, so I know what and why I am saying. Most of them speak by themselves in the published figures. However, they have a few characteristics that make this assemblage suitable for criticism. “

The study’s main focus lies almost exclusively on flaked stone tools retrieved from the Mexican cave. Unlike Clovis points that are made from chert or obsidian, the tools found at Chiquihuite are made from a particular variety of limestone — “greenish and finely grained, recrystallized, which makes it behave just like chert,” Ardelean said.

Judging from the geology of the cave, the limestone for these tools must have been sourced elsewhere, outside the cave. Limestone is a rather abundant raw material for stone tool manufacturing, so it is not at all unusual to see it there.

“The Chiquihuite assemblage could be defined as a microlithic technology, dominated by microblades, microlith fragments and transversal flakes. Also, by transversal points made by the superficial modification of transversal flakes,” said Ardelean.

As for what these early hunter-gatherer populations must have looked and socialized like, there is not much to draw inferences from, unfortunately. The researchers were not able to extract human-environmental DNA (eDNA) from the Mexican cave, which would have helped pinpoint the lineage of the cave’s inhabitants.

“I think there were very few humans in the Americas during the LGM and before. Literally a few small groups scattered across such a large territory. That makes them very difficult to find, and, when found, their traces are very scant. These ancient groups were nomads and they did not live for too long in the same location. They migrated in wide circular migration cycles, returning to a determined location after years or generations. They probably revisited Chiquihuite Cave every certain number of years and remained there for a few weeks only, maybe during winters, before moving on,” Ardelean said.

“I also think that many LGM human groups went extinct, they were lost migrations that died out and did not pass their genetic and cultural legacy to the later populations. That makes them even more difficult to find and trace,” he added.

More than 40 archaeological sites in North America and Beringia point to pre-Clovis human presence4

Map showing the location of the 42 archaeological sites. Credit: Nature, Becerra-Valdivia et. al.

Chiquihuite cave is just the latest addition to a roster of archaeological sites that support a much earlier human dispersal into the Americas than it is currently established.

Another study published today in Nature, led by Lorena Becerra-Valdivia, an archaeological scientist at the University of New South Wales and the University of Oxford, and Thomas Hingham from the Research Laboratory for Archaeology and History of Art at the University of Oxford, shows that by at least 15,000 years ago, the North American continent was already widely settled.

The authors’ statistical analysis and radiocarbon dating, which required years of research and were very laborious, imply that some archaeological sites were settled even far earlier than that.

For instance, six Brazilian sites — five in the state of Piaui and the other one in Moto Grosso — are more than 20,000 years old. Clearly, humans must have migrated from Asia much earlier than that.

“The results of our study show that whilst there were humans in North America before, during and immediately after the Last Glacial Maximum, populations expanded significantly across the continent much later, during a period of abrupt global climate warming at the end of the Ice Age, beginning at around 14,700 years ago. This is based on the synchronous start of three major stone tool traditions (Clovis, Western Stemmed and Beringian), a spike in archaeological sites and chronological data, as well as genetic evidence pointing to marked population growth,” Becerra-Valdivia told ZME Science.

Becerra-Valdivia, who is Ardelean’s co-author in the accompanying Nature paper, also visited Chiquihuite cave as part of her research, which encompassed 42 archaeological sites in North America and Beringia.

“One of my highlights was a visit to Chiquihuite Cave, after a four-hour-long foot journey. Having the opportunity to see the site and evidence first hand is invaluable to a radiocarbon expert. It helps us better understand the archaeological site and makes us appreciative of the work that archaeologists do in the field,” she said.

“The accompanying paper is a marvelous piece of work that I enjoyed very much. The authors are also co-authors of my paper. Lorena and Tom are very good colleagues and dear friends of mine, and I have known them for years. I have a profound respect for their talent and geniality with radiocarbon dating. Their paper gives us the best image of the accurate dates of the early sites and it will be a referent for years to come,” Ardelean said.

The ages of the various archaeological sites identified by the study. Most pre-date Clovis by thousands of years. However, no other site comes close in dating to Chiquihuite Cave. Credit: Nature, Becerra-Valdivia et. al.

For most of the last major glacial advance, the entry point through the Bering Strait was blocked by ice sheets. This is the main reason why a much earlier timeline of pre-Clovis migration has been hard to swallow for the research community at large.

Becerra-Valdivia and Hingham have proposed an alternative route down the Pacific coast, which is supported by archaeological findings in coastal zones. However, validating this model will prove challenging in the future as it is likely that the earliest coastal-entry archaeological sites are now submerged offshore.

“Given that humans were already present in the continent between 33 and 31 thousand years ago (at Chiquihuite Cave), the initial crossing from Asia must have occurred earlier. We suggest that this likely occurred at the end of a period called Marine Isotope Stage 3 (between 57 and 29 thousand years ago), when ancient Beringia was either completely or partially submerged under water. Therefore, the journey must have required a degree of maritime or littoral (coastal) adaptation,” Becerra-Valdivia told me in an email.

The highly precise radiocarbon dating of the archaeological sites overlaps with the latest dates of the appearance of 18 now-extinct fauna genera. The end of the last ice age was a period of intense climate change, which is believed to have brought the demise of many species. But the role that human intervention had in these extinctions may have been important.

“The expansion of humans during GI-1 seems to have played a role in the decline of large megafauna, including types of camels, horses and mammoths, who disappear within this and an immediately preceding, colder period. The contribution of climate change in faunal extinctions cannot be excluded, however,” said have required a degree of maritime or littoral (coastal) adaptation,” Becerra-Valdivia.

Both studies make valuable contributions to the ongoing debate of how humans first settled the Americas. They are also likely to be met with quite a bit of skepticism — and rightfully so. There’s no other site that comes close to the early timeline of the Chiquihuite Cave, and this is a problem. However, perhaps other similarly ancient sites may be discovered in due time in North America as more investigations are performed.

“We are starting now to analyze the materials from the very last excavation at the cave, done in 2019. We will study new artefacts and other materials with new techniques and involving new proxys. Hopefully, within a year or so, we’ll be able to submit a second paper about Chiquihuite, with new data and with an improved resolution,” Ardelean said.

“Future research is required in South America. Only by unlocking the history of initial human occupation there will we be able to see the entire picture and understand the full migration pattern,” Becerra-Valdivia added. “These are paradigm-shifting results that shape our understanding of the initial dispersal of modern humans into Americas. They suggest exciting and interesting possibilities for what likely was a complex and dynamic process.”

A 15,000 year old stemmed point. Credit: Texas A&M University.

Scientists find oldest weapons in North America, questioning the timeline of the continent’s colonization

A 15,000 year old stemmed point. Credit: Texas A&M University.

A 15,000-year-old stemmed point. Credit: Texas A&M University.

While digging at a site in Central Texas, archaeologists have come across a stockpile of ancient weapons. Dating of the sediment from which the spears and other tools were unearthed suggests the artifacts are 15,500 years old. That’s much older than artifacts found at Clovis sites, long believed to be the first culture that colonized the Americas.

Different shape, different timeline

The projectile points found at the Debra L. Friedkin site in Texas are made of chert. What’s immediately apparent is that their shape is very distinct from the Clovis-style lanceolate (leaf-shaped) fluted projectile point with concave bases. Instead, the newly-identified technology features triangular projectiles.

“There is no doubt these weapons were used for hunting game in the area at that time,” said Michael Waters, professor of anthropology at Texas A&M and lead author of the new study, said in a statement. “The discovery is significant because almost all pre-Clovis sites have stone tools, but spear points have yet to be found. These points were found under a layer with Clovis and Folsom projectile points. Clovis is dated to 13,000 to 12,700 years ago and Folsom after that. The dream has always been to find diagnostic artifacts – such as projectile points – that can be recognized as older than Clovis and this is what we have at the Friedkin site.”

Water and colleagues uncovered a staggering trove of 100,000 artifacts, including 328 tools and 12 complete and fragmented projectile points. Using optically stimulated luminescence on sediments — a dating method that measures the amount of light emitted from energy stored in certain rock types and derived soils — they determined the artifacts were between 13,500 and 15,500 years old.

Other projectiles found at the Friedkin site.

Other projectiles found at the Friedkin site.

It’s possible that the weapons were fashioned by people belonging to an earlier, separate migration into the Americas. The earliest artifacts belonging to the Clovis culture, a prehistoric Paleo-Indian culture, are dated to about 13,000 years ago — this evidence was previously thought to reflect the earliest occupation of the Americas. It is thought that the Clovis arrived in North America via an ice-free corridor through glacier-covered Alaska and western Canada.

Clovis points are found in association with the bones of Ice Age animals in sites in many areas of North America and document both the importance of big game hunting and the effectiveness of early Palaeo weaponry. The species exploited included mammoths, who grazed on the tundra grasses and mastodons who browsed on the spruce needles. Giant, long-horned bison provided a secondary food source.

There’s another distinct style of spear point technology, the Western Stemmed Tradition, whose points were leaf-shaped like Clovis, but which were tapered at the base instead of being fluted. The oldest Western Stemmed Tradition artifacts are dated to close to the earliest ones of the Clovis variety, circa 13,000 years ago. Some archaeologists argue that Western Stemmed Tradition precedes Clovis.

Excavations at the Debra L. Friedkin site 2016. Credit: Center for the Study of the First Americans, Texas A&M University.

Excavations at the Debra L. Friedkin site 2016. Credit: Center for the Study of the First Americans, Texas A&M University.

Scientists have always wondered if there was any connection between Clovis and Western Stemmed Tradition cultures. The new study certainly complicates things, suggesting that the technology found at Friedkin was a precursor. Alternatively, Clovis and Western Stemmed Tradition may have appeared from a second wave of migration that brought with it the leaf-shaped points.

More excavations and alternative dating methods of Friedkin artifacts might shed more light on the matter.

“The findings expand our understanding of the earliest people to explore and settle North America,” Waters said. “The peopling of the Americas during the end of the last Ice Age was a complex process and this complexity is seen in their genetic record. Now we are starting to see this complexity mirrored in the archaeological record.”

Scientific reference: Michael R. Waters et al. Pre-Clovis projectile points at the Debra L. Friedkin site, Texas—Implications for the Late Pleistocene peopling of the Americas, Science Advances (2018).

Photo: Texas A&M Universit

Skeleton remains prove first North American settlers came from Asia

The genome sequence of the Ice Age skeletal remains of a 1-year-old boy gave scientists tantalizing proof that the first settlers in North American originated in Asia, and not from Europe as some theories might suggest. The boy belong to a group of people known as the Clovis, the direct ancestors of modern day North American natives.

The remains of the Clovis child were first unearthed in 1968 near a rock cliff in Montana. At the burial site, thought to be some 12,600 years old, anthropologists also found 100 artifacts, including spear points and antler tools. In fact, the Clovis culture is widely known and recognized for its prolific use of tools. They’re the inventors of the the ‘Clovis point,’ a spear-shaped weapon made of stone that is found in Texas and other portions of the United States and northern Mexico. These weapons were used to hunt animals, including mammoths and mastodons, from 13,000 to 12,600 years ago.

Photo: Texas A&M Universit

Photo: Texas A&M Universit

Michael Waters, director of the Center for the Study of First Americans at Texas A&M, is part of the team that sequenced the genome of the skeleton remains. The analysis, by now standard, showed that the child and its forefathers no less, originated from Asia. This was widely considered of course, the leading theory being that ancient North American ancestors arrived at the continent by crossing a link between Asia and Alaska.

“We hope that this study leads to more cooperation between Native Americans and scientists. This is just one human genome. We need to know the genetic story of modern Native peoples and derive more genetic data from ancient remains to fully understand the origins and movements of the First Americans and their descendants,” Waters adds.

The Crow Tribe will oversee the the reburial of the remains in accordance with Native rituals in the near future, Waters also said.

“The genetic information provided by the Anzick boy is also part of the larger story of modern humans. We know that modern humans originated in Africa and then around 50,000 years ago spread rapidly over Europe and Asia.  The last continent explored and settled by modern humans were the Americas.  In essence, the Anzick boy tells us about the epic journey of our species,” he adds.


The high temperatures of the meteorite impact 12,900 years ago produced mm-sized spherules of melted glass with the mullite and corundum crystal structure shown here Photographed by: Mukul Sharma

Meteor impact in Canada may have triggered the Big Freeze that caused mass extinction and forced humans into agriculture

The high temperatures of the meteorite impact 12,900 years ago produced mm-sized spherules of melted glass with the mullite and corundum crystal structure shown here Photographed by: Mukul Sharma

The high temperatures of the meteorite impact 12,900 years ago produced mm-sized spherules of melted glass with the mullite and corundum crystal structure shown here
Photographed by: Mukul Sharma

A recent study has revived an older controversy, after  Dartmouth Professor Mukul Sharma and his team reported what they claim is the first conclusive evidence that links an extraterrestrial impact in Canada with the beginning of the Younger Dryas, a period of abrupt climate change that caused major cooling through the Earth. During this time, a number of species became extinct and the human hunger-gatherer population transitioned to an agricultural based lifestyle.

In the 1.5-billion-year-old Quebecia terrane in northeastern Canada, near the Gulf of Saint Lawrence and modern day Quebec, researchers believe a comet or meteor impact took place, after at they analyzed the chemical composition of spherules discovered at the location (droplets of solidified molten rock expelled by the impact of a comet or meteor). The chemical composition matched those of spherules  deposited in Pennsylvania and New Jersey at the start of the Younger Dryas period.

The Younger Dryas or the Big Freeze as its also been called began some 12,900 years ago and enveloped the world in a short lasting (in geological terms – some 1,000 years) glacial period. During this time, a number of species became extinct, including saber-toothed cats, giant sloths, and mastodons. The same event marked the end of the Clovis hunter-gatherer culture in favor of the adoption of farming and animal husbandry, as supported by evidence dated from the time collected from the Near East – coincidentally or not the region was also home to the earliest city settlements we know of (Ur, Uruk).

“The Younger Dryas cooling impacted human history in a profound manner,” says Dartmouth Professor Mukul Sharma, a co-author of the study. “Environmental stresses may also have caused Natufians in the Near East to settle down for the first time and pursue agriculture.”

The newly discovered spherules do not originate from the 4km-wide Corossal crater – a known impact crater in Quebec. This fact leads the researchers to conclude that a series of comet or meteor impacts caused the beginning of the Younger Dryas 12,900 years ago. The meteor/compact impact theory sparking the Younger Dryas isn’t new and has for a long time been contested. The current accept theory is that an ice dam rupture released huge amounts of freshwater into the Atlantic. This in turn was thought to have shut down ocean currents moving warm tropical water, resulting in colder conditions.

“It may well have taken multiple concurrent impacts to bring about the extensive environmental changes of the Younger Dryas,” says Sharma. “However, to date no impact craters have been found and our research will help track one of them down.”

Worth noting is that ZME Science reported earlier of a newly discovered meteor impact site in Mexico dating from 13,000 years ago, where an eclectic geological mix of materials, including nanodiamonds, impact spherules, and more, which, according to the researchers, are the result of a cosmic body impacting Earth.  Apart from the Mexican site, the researchers also identified sediment layers of the same age, dating back 13,000 years ago,  in Canada, the United States, Russia, Syria and various sites in Europe.

Findings appeared in the journal PNAS.

A new model of flood waters from melting of the Laurentide Ice Sheet and large glacial lakes along its edge that covered much of North America from the Arctic south to New England over 13,000 years ago, shows the meltwater flowed northwest into the Arctic first. This weakened deep ocean circulation and led to Earth’s last major cold period.The direction of meltwater drainage is shown by the yellow arrows. The approximate position of the ice sheet is shown (in white) just before the onset of the Younger Dryas. The ocean colors are surface salinity from the control integration with warm (cold) surface currents shown in red (blue). (c) Alan Condron, UMass Amhers

Trigger for Earth’s last ‘big freeze’ located by geoscientists

Some 12,900 years ago, a massive flood of melted freshwater in the Arctic caused a 1,200-year-long chill nicknamed the “Big Freeze.” During this time much of the Northern Hemisphere was engulfed by centuries of cold, which caused the extinction of most great mammals, like mammoths, as well as the Clovis people. For decades, scientists have been debating from where and how did the freshwater flood flow. Now, a team of scientists may have finally reached a conclusion after they devised a computer model.

Technically known as the Younger Dryas, this specific period wasn’t a glacial period or what’s commonly referred to as an “ice age”, since it was a cold time in an otherwise warm span between ice ages. In other words, the Big Freeze wasn’t part of the Earth’s natural warm/cold cycle, it was triggered by an event. Previous theories held that a cosmic impact caused the Big Freeze, however recently scientist have reached to a common conclusion that a vast pulse of freshwater is to blame.

A new model of flood waters from melting of the Laurentide Ice Sheet and large glacial lakes along its edge that covered much of North America from the Arctic south to New England over 13,000 years ago, shows the meltwater flowed northwest into the Arctic first. This weakened deep ocean circulation and led to Earth’s last major cold period.The direction of meltwater drainage is shown by the yellow arrows. The approximate position of the ice sheet is shown (in white) just before the onset of the Younger Dryas. The ocean colors are surface salinity from the control integration with warm (cold) surface currents shown in red (blue). (c) Alan Condron, UMass Amhers

A new model of flood waters from melting of the Laurentide Ice Sheet and large glacial lakes along its edge that covered much of North America from the Arctic south to New England over 13,000 years ago, shows the meltwater flowed northwest into the Arctic first. This weakened deep ocean circulation and led to Earth’s last major cold period.The direction of meltwater drainage is shown by the yellow arrows. The approximate position of the ice sheet is shown (in white) just before the onset of the Younger Dryas. The ocean colors are surface salinity from the control integration with warm (cold) surface currents shown in red (blue). (c) Alan Condron, UMass Amhers

The source of this great flood was the massive glacial Lake Agassiz, located along the southern margin of the Laurentide Ice Sheet, which at its maximum 21,000 years ago was 6,500 to 9,800 feet (2,000 to 3,000 meters) thick and covered much of North America, from the Arctic Ocean south to Seattle and New York. Researchers believe the flood was caused by a sudden melting of an ice dam. The subsequent massive influx of freshwater diluted the circulation of saltwater in the North Atlantic, disrupting the ocean “conveyer belt” that transports heat to Europe and North America. The weakening of this circulation caused by the flood resulted in the dramatic cooling of North America and Europe.

Until recently, however, scientists weren’t sure whether the meltwater flowed northwest into the Arctic first, or east via the Gulf of St. Lawrence.

“This episode was the last time the Earth underwent a major cooling, so understanding exactly what caused it is very important for understanding how our modern-day climate might change in the future,” says Condron of UMass Amherst’s Climate System Research Center

Working with Peter Winsor at the University of Alaska, Condron used a high resolution, global, ocean-ice circulation model that is 10 to 20 times more powerful than previously attainable, to compare how different drainage outlets was delivered to the sinking regions in the North Atlantic. If Lake Aggasiz drained into the North Atlantic down the St. Lawrence River then the thermohaline circulation would have weakened by less than 15 percent. In contrast, when the meltwater first drains into the Arctic Ocean, narrow coastal boundary currents can efficiently deliver it to the deep water formation regions of the sub-polar north Atlantic, weakening the thermohaline circulation by more than 30 percent.

These findings hint that shifts in the flow of water in the Arctic could dramatically alter today’s climate.

“However, in our modern-day climate, there are no sources of freshwater as large as the glacial lakes or Laurentide Ice Sheet readily available to suddenly flood into the ocean,” Condron said. “As a result, we should be cautious using this study as an analog for what might trigger modern-day abrupt climate change.”

The researchers are able, however, to put their model to good use in other instances, though far less extreme, like studying the effects of the potential melting of large ice sheet over Greenland and changes in the hydrological cycle, such as increased river runoff of the Arctic in the near-future.

Findings were published in the journal Proceedings of the National Academy of Sciences.

Source: University of Massachusetts at Amherst

Three bases for Western Stemmed projectiles from the Paisley Caves in Oregon. The bases date to some 13,000 years ago. (c) Jim Barlow

Archaeological evidence attests second founding group in North America, besides Clovis culture

Scientists from U.S., Britain and Denmark have recently reported in a new study that conclusive evidence, in the form of stone tools and human DNA, attests the presence of a second stone age culture in North America, separate from the Clovis culture, the earliest human society discovered and confirmed thus far.

Three bases for Western Stemmed projectiles from the Paisley Caves in Oregon. The bases date to some 13,000 years ago. (c) Jim Barlow

Three bases for Western Stemmed projectiles from the Paisley Caves in Oregon. The bases date to some 13,000 years ago. (c) Jim Barlow

The findings were made in Paisley Caves, on the east side of the Cascade Range, near the town of Paisley a few years ago, but only after extensive analysis and scrutiny could the researchers make this pertinent conclusion. One that significantly changes anthropologists’ view of North American stone age civilization dispersion and human migration patterns in the continent. According to the scientists, the two cultures, Paisley and Clovis, the latter of which is named after the town of Clovis, Mexico where the first findings were made at the time, shared the continent more than 13,000 years ago.

The Clovis culture found in the southeast and interior U.S employed elegantly chipped stone points, whose bases are distinctly concave where they were tied to the wooden shafts of spears or throwing darts for hunting. At Paisley, archaeologists found narrow-stemmed spear points shaped by different flaking techniques – very much dissimilar to those found in Clovis, from roughly the same period. The researchers suggest that two groups coexisted independently on the continent.

“These two distinct technologies were parallel developments, not the product of a unilinear technological evolution,” the research team, led by Dennis L. Jenkins of the University of Oregon, concluded in the report. “The colonization of the Americas involved multiple technologically divergent, and possibly genetically divergent, founding groups.”

Until now, most western stemmed projectiles with accurate dating have been younger than Clovis artifacts, leading to theories the two technologies evolved from a single source. These latest findings seem to point towards an opposite direction.

Besides the stone points, the scientists involved in the study also studied the DNA found in coprolites, or dried feces, found in the cave, which pointed to Siberian-East Asian origins of the people.

“We seem to have two different traditions coexisting in the United States that did not blend for a period of hundreds of years,” Dr. Jenkins said.

DNA cannot be directly dated with radiocarbon technology, however the researchers instead used the fibers from the coprolites, residue of the food the cave dwellers had eaten, to date them. Any contaminating carbon was washed out of the coprolites with distilled water. In the end, the scientists found that some coprolite samples, along with one of the Western Stemmed points, was dated to 13,000 to 13,200 years ago. So far, the researchers have extracted only mitochondrial DNA, which is inherited from the mother, but this “definitely suggests,” he said, that these people were from Asia and could be related to today’s Native Americans.

“We are trying to retrieve nuclear DNA from the site,” he added, which should provide more precise information about who are the “closest contemporary people” associated with the cave dwellers.

The findings were reported in the journal Science.

source: NY TIMES