The First People of Americas

Author : Wahid Ahmad Share

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Chiquihuite Cave is located high in the Astillero Mountains of Zacatecas, Mexico, at an altitude of 2,740 meters. It is about 1,000 meters above the surrounding valley. The cave was formed millions of years ago from ancient limestone and features two large chambers that are more than 50 meters wide and 15 meters tall. The floor of the cave is covered in debris from roof collapses and mudslides, which sealed it off by the end of the Ice Age

researchers have uncovered layers of soil and artifacts and found signs of human activity in the cave, dating back to the Ice Age, roughly 26,000 to 18,000 years ago. These layers show a pattern of changing wet and dry conditions over time. What's important is that the layers were not disturbed, meaning they have remained in their original position.

Two layers of soil stood out in particular, a thick orange-brown layer that separates older deposits (from the Ice Age) from newer ones (after the Ice Age). A hardened surface above Layer 1212, which suggests a dry, stable period at the end of the Ice Age. These stable times may have been when humans lived in the cave, as conditions were more favourable.

During the coldest parts of the Ice Age, the area near the cave was forested with trees like juniper, fir, pine, and spruce. As the climate warmed, these forests gave way to open areas with Joshua trees and grasses. DNA from the cave soil also revealed the presence of animals like bats, rodents, bears, and goats.

Burnt plants and charcoal suggest that early humans used fire, possibly for cooking or staying warm. Researchers also found stone tools made from carefully chosen rock, showing that these people were skilled and resourceful.

Stone tools were found in the cave; include scrapers, blades, and knives, made by chipping stones to create sharp edges. The tools were crafted from green and black limestone, which was stronger and easier to work with than the gray limestone inside the cave. The people who lived here seemed to have a deep understanding of their environment and selected materials carefully.

The tools were unique, showing a style not seen in other ancient cultures in the Americas, reflecting the creativity and ingenuity of the cave's inhabitants.

While no human DNA was found, other clues suggest human presence. Burnt remains of plants, ash, and traces of fire all point to human use of the cave. Chemical residues in the soil and the many stone tools are additional evidence of their activities.

Over thousands of years, the cave’s surroundings shifted from dense forests during the Ice Age to grassy open areas as the climate warmed. DNA from ancient horses and modern horses also revealed how animals changed in response to these shifts.

However, the hypothesis that Chiquihuite Cave shows evidence of early human presence in the Americas and unique stone tool industry is unconvincing. The stone pieces they describe as tools could have formed naturally due to the conditions in the cave, where rocks frequently break apart. This possibility was not thoroughly explored in their study.

There is lack of enough evidence to prove that the stones were shaped by humans. More detailed work is needed to show that these stones are not just naturally broken rocks but were purposefully made by people. We are open to changing our opinion if stronger evidence is provided.

The claim that humans lived in the cave as far back as 33,000 years ago challenges existing understanding of how and when people first arrived in the Americas. However, there is no clear evidence of human activity, such as tools, structures, or remains, in the cave. The lack of connections to known ancient populations also makes this claim less convincing.

Until stronger evidence is presented, it is too early to change our understanding of early human migration to the Americas based on Chiquihuite Cave.

The question of when, how, and by whom the Americas were first inhabited has been a long-standing and highly debated topic in archaeology.

Scientists have been intrigued by key questions: When did humans first arrive in the Americas? What kind of people were they? And what route did they take to reach the New World?

These queries have fascinated researchers since Columbus landed in the Bahamas in 1492. This chapter explores these controversies and sheds light on the diverse societies of later hunter-gatherers in the Americas.

Many archaeologists initially believed that the first humans in the Americas entered through the Bering land bridge when it was still above water. Intense debates exist regarding the specifics of human settlement in the Americas.

Controversies revolve around three fundamental questions.

How long ago did humans first settle in the Americas? What tools did they bring, and what was their way of life? What was the ancestral origin of the first Native Americans?

Even after the discovery of Folsom excavations, controversies surrounding the initial settlement of the Americas have persisted and continue to be one of the most vigorous debates in the field.

The Folsom excavations refer to a significant archaeological discovery in Folsom, New Mexico, that dramatically altered our understanding of early human life in North America. The Folsom site, excavated in the late 1920s, revealed evidence of early humans hunting now-extinct species of bison, using a distinct style of projectile points—called Folsom points. These finely made, fluted spear points were found embedded in the bones of Bison antiquus, a larger relative of the modern bison, establishing a clear connection between humans and these animals.

The discovery was groundbreaking because it pushed back the timeline for human presence in North America to over 10,000 years ago, dating to the Paleo-Indian period (around 10,000 to 8,000 BCE). Before the Folsom excavations, it was commonly believed that humans had only arrived in the Americas around 4,000 to 5,000 years ago. The careful association of stone tools with extinct animals provided the first conclusive evidence of human activity in the continent during the late Pleistocene.

The Folsom site is now considered one of the most important archaeological finds in the history of North American prehistory, and it contributed to the identification of the Folsom culture, which is distinct from the later Clovis culture.

But just a few years later, another discovery would push the boundaries of our understanding even further. In Blackwater Draw, near Clovis, New Mexico, archaeologists found even older tools—massive, fluted spear points used to hunt mammoths and other Ice Age megafauna.

These Clovis points, dating back 13,000 years, revealed the existence of an ancient culture that spread across much of North America. The precision of the tools and their wide distribution suggested a highly organized, mobile society of hunter-gatherers.

Until recently, the widely accepted theory about the first humans in the Americas suggested that big-game hunters arrived around 13,000 years ago from Asia, crossing through a corridor between ice sheets.

Once below the 48th parallel north, it was thought that these people developed the 'Clovis' tradition, dated to around 13250-12800 years ago, which spread across North America.

This idea, known as the 'Clovis-first' model, dominated much of the 20th century. However, new archaeological evidence has challenged this theory, revealing sites and technological industries that predate Clovis.

As a result, the earlier narrative has been debunked, and a new perspective suggests that an earlier dispersal route along the Pacific Coast is the more likely means by which humans initially entered the Americas.

Around 13,000 to 13,500 years ago, people had spread across both North and South America, with a unique group known as the Clovis culture emerging in what is now the southeastern and southwestern United States.

The Clovis people are best known for their distinct stone tools, particularly their fluted lanceolate points, which were carefully crafted through a technique called bifacial reduction. These tools were highly effective for hunting, and the Clovis culture became widely recognized for this technological advancement.

Another key aspect of their toolkit was the core-and-blade technology, where large blades were made from special cores and then used as tools or left unmodified.

While there’s debate about whether this technology originated in Eurasia or evolved independently in America, it’s clear that the signature Clovis point was an American innovation.

Early discoveries of Clovis tools were often associated with the hunting of large Ice Age animals like mammoths, leading early archaeologists to label the Clovis people as big game hunters.

Famous sites like Blackwater Draw in New Mexico and Murray Springs in Arizona revealed evidence of such hunts, but these megafaunal kill sites were actually quite rare.

As more Clovis sites were discovered—such as base camps like the Gault site in Texas—it became evident that Clovis people had a broader diet than previously thought. They hunted small game and likely gathered plants as well.

This more varied subsistence strategy challenges the idea that they were primarily focused on large prey, though hunting mammoths and other big animals still played a significant role in their lifestyle.

Clovis technology is mostly concentrated in southeastern North America, but it also spread to other regions, including the Great Plains and even as far as Alaska. Some researchers suggest that these widespread Clovis artefacts could have been the result of people moving across the continent, while others think it might simply reflect the spread of technology through trade or cultural diffusion.

For years, archaeologists believed the Clovis culture spanned from about 13,400 to 12,800 years ago. However, more recent studies suggest it might have been much shorter—perhaps only lasting 200 to 300 years.

This idea sparked debate because such a short time frame seems too brief for the Clovis people to spread their culture across such vast distances. While some sites, like Aubrey in Texas, suggest an earlier timeline, the exact duration of the Clovis period remains unresolved.

Evidence from northern Mexico, including a gomphothere (a prehistoric elephant-like creature) kill site, hints that Clovis culture might have originated further south than previously thought, possibly evolving from existing forager populations.

Some researchers also propose that early Clovis groups may have travelled along the Pacific Coast before moving inland, shaping the early human presence in North America. The debate over the origins and spread of Clovis culture continues, but it remains a key chapter in the story of the first Americans.

In western North America, a distinct tool-making tradition, called the Western Stemmed Tradition existed during the same period as the Clovis culture, if not earlier.

Unlike Clovis points, which are fluted at the base, Western Stemmed Tradition points were stemmed, with ground edges, and were typically made from volcanic stones like obsidian. These tools came in various forms and were made using different techniques than Clovis tools, lacking the overshot thinning seen in Clovis bifaces.

A unique feature of Western Stemmed Tradition culture is the use of crescent-shaped bifaces, thought to have been used as projectile points. Their exact purpose is unclear, though some researchers suggest they may have been used to hunt marsh birds.

Most Western Stemmed Tradition sites are found around what were once lakes, rivers, and wetlands, particularly in the Great Basin, Columbia River drainage, and along the Pacific coast.

Unlike Clovis people, who are associated with hunting large animals like mammoths, Western Stemmed Tradition populations appear to have focused on smaller game, fish, and plant-based diets, living in areas with abundant water resources.

 

The Western Stemmed Tradition people are referred to as “Paleoarchaic,” indicating a different lifestyle from their Eastern counterparts, like the Clovis people.

Western Stemmed Tradition artefacts have been found across a wide range of environments, from the Rocky Mountains to Baja California, and as far north as Alaska and British Columbia.

The timeline of Western Stemmed Tradition is still debated. Some researchers argue that the Western Stemmed Tradition existed alongside the Clovis culture, while others think Western Stemmed Tradition could be even older.

For example, at sites like Smith Creek Cave and Bonneville Estates Rockshelter, Western Stemmed Tradition points were found with early radiocarbon dates, suggesting that these people lived during the same time as Clovis populations.

There is also evidence from sites like Paisley Caves in Oregon and Cooper’s Ferry in Idaho, where Western Stemmed Tradition points have been dated to around 13,000 years ago, overlapping with the Clovis period.

The exact origin of Western Stemmed Tradition technology is still unclear. It’s possible that both Clovis and Western Stemmed Tradition technologies developed independently in different parts of the world or that they evolved from an even earlier tool-making tradition.

Regardless, the evidence suggests that the Western Stemmed Tradition and Clovis cultures existed at roughly the same time, each with its own distinct way of life and tool-making techniques.

The early human occupation of South America around 13,000 to 13,500 years ago is challenging due to the continent’s diverse landscapes, cultures, and technologies. In general, there were two main tool-making traditions during this time: the "Bifacial Tradition" and the "Edge-Trimmed Tradition."

the The Bifacial Tradition is known for its “Fishtail” and “El Jobo” points, which are similar to Clovis and Western Stemmed points, being bifacially worked and sometimes fluted. The Edge-Trimmed Tradition, on the other hand, focused on simpler unifacial tools made from cores and flakes.

These tools have been found from northern South America all the way down to the southern tip, and there’s some evidence of similar traditions in the eastern parts of the continent.

The Fishtail points, found in southern South America, seem to have been produced by people who hunted megafauna like ground sloths and horses. However, direct evidence linking these tools to megafauna hunting is limited.

By 13,000 years ago, the people of South America had adapted to a variety of environments, including coastal, mountainous, and tropical regions, each with its own subsistence strategies.

Fishtail points, knives, scrapers, and other tools were widely used, and many sites without these distinctive points suggest other groups were also present at the time.

There’s an ongoing debate about the origins of these South American tool traditions. Some researchers think they evolved from North America’s Clovis culture, while others argue they developed independently in South America, with the earliest Fishtail sites in the southern part of the continent.

Notably, the Fishtail sites in Chile and Argentina date back to around 13,000 years ago, suggesting a long history of human presence in these areas.

Other early sites, even those without diagnostic points, suggest widespread human activity across South America by this time. For example, sites in Argentina, Chile, Peru, and Brazil all have radiocarbon dates around 13,000 years ago, showing a broad and diverse occupation of the continent.

These findings overlap with the later part of the Clovis period in North America, indicating that people were well-established in South America around the same time.

Between 29,000 and 24,000 years ago, the Earth entered a colder climatic period known as the Last Glacial Maximum, which marked the peak of the last ice age. This period, saw a significant drop in temperatures, especially in regions like northeast Asia and North America. The ice sheets of North America, particularly the Laurentide and Cordilleran ice sheets, reached their maximum extent between 25,000 and 17,000 years ago. This created massive barriers for human migration, such as an ice-free corridor between these ice sheets that was closed off by around 20,000 years ago.

With regard the timing of the initial peopling of the Americas three models have been proposed. The Strict Clovis-First Dispersal model posits that humans arrived only after the development of the Clovis culture around 13,000 years ago

This model faces challenges because archaeological evidence from sites older than 13,000 years suggests earlier human presence in the Americas.

The Paleo-Indian Dispersal model, which suggests humans arrived after the Last Glacial Maximum, around 16,000 years ago, has gained the most support. This model aligns with genetic and archaeological evidence, indicating a gradual migration into the Americas before the Clovis period, though not as early as proposed by some controversial sites.

The Pre-Paleo-Indian Dispersal model argues for an even earlier human presence, before 16,000 years ago. However, it faces significant challenges due to a lack of strong genetic evidence. If this model were accurate, it would require the existence of populations that were genetically unrelated to modern Native Americans, which conflicts with current genetic data showing Native Americans diverged from East Asians between 26,000-20,000 years ago.

By around 13,000 to 13,500 years ago, people were spread across North and South America, adapting to various environments and using different subsistence strategies and toolkits.

This period marks the youngest point of the framework for the first human occupation of the Americas. However, since these sites were already occupied by that time, it raises the question: how long did it take for humans to spread so widely and develop such diverse cultures?

Experts generally agree that it would have taken at least 500 to 1,000 years, if not longer, for small groups of foragers to spread across the continents and create the distinct technologies and ways of life seen at these early sites.

Therefore, based on the most widely accepted early cultural traditions, it seems reasonable to use 14,000 years ago as a starting point for human migration into the Americas.

In recent decades, genetic studies have become a key tool in understanding the origins of Native Americans. Mitochondrial and Y-chromosome haplogroups in Native American populations suggest that the ancestors of Native Americans most likely originated in the Altai Mountains region of south-central Siberia, near the borders of Russia, China, and Mongolia.

 

However, this conclusion comes with uncertainties. The identification of this origin is based on the assumption that populations have not moved significantly over the last 30,000 years. But genetic evidence shows that populations in Eurasia moved in many directions during the last Ice Age. Some groups stayed in place, others moved to new areas, and populations mixed and split over time.

 

For example, DNA from an ancient burial site in Malta (near Lake Baikal in Siberia) dating back 24,000 years reveals a population called the Ancient North Eurasians. This group was genetically related to both Native Americans and Europeans but had already diverged from East Asians. Another burial site, Ust'-Ishim, in western Siberia, shows a population that split off from ancestors of modern West and East Eurasians around 45,000 years ago.

 

Despite these findings, there is still no clear picture of how these ancient populations migrated to the Americas. Some evidence suggests a possible connection to populations in Europe because a particular mitochondrial DNA haplogroup, X2a, found in Native Americans, is also found in Europeans. However, this connection is not fully understood, and X2a could have originated from anywhere in Eurasia.

 

 

Ancient North Siberians from Malta diverged from West Eurasian populations about 39,000 years ago and disappeared as a separate population, leaving genetic traces in later ancient and present-day groups, especially among Native American populations.

 

Around 23,000-20,000 years ago, there was gene flow between the Ancient North Siberians group and an East Asian group.

 

This interaction led to the formation of at least two distinct lineages: the Ancient Palaeo-Siberians in northeast Siberia and the basal American branch, whose descendants eventually crossed to the Americas.

 

The timing of the basal American branch's formation is uncertain. One hypothesis suggests it occurred after the Last Glacial Maximum, around 18,000 years ago.

However, the exact timing remains unclear, and it's possible that gene flow occurred even before 24,000 years ago, as long as it happened after the population represented by Malta diverged from the population represented by Afontova-Gora 3.

 

The emergence of the basal American branch must have occurred before approximately 21,000 to 20,000 years ago, indicating admixture before the Last Glacial Maximum. Native American individuals show ancestry from Ancient North Siberians and East Asian populations, suggesting early geographical isolation, possibly in western Beringia or further south.

 

Based on the Beringian standstill model, dispersal into the Americas did not happen immediately but followed an extended pause, possibly in the region of the Bering land bridge.

 

From the isolated population of Ancient North Siberians several lineages emerged, Ancient Beringian individuals, and Ancestral Native American individuals. These populations crossed into North America in separate movements, with Ancient Beringians disappearing around 9,000 years ago.

Although Ancient Beringians did not continue farther south, they are genetically closer to other past and present Native American individuals than to any other contemporary population.

 

The idea of "Beringian standstill" is based on genetic changes observed in North American populations, suggesting that these ancestors diverged from their Eurasian relatives thousands of years before entering the Americas.

 

Researchers proposed that this genetic bottleneck likely occurred in Beringia, setting the stage for a rapid spread of these populations into the Americas after the Last Glacial Maximum.

 

However, if there's no solid evidence for a population residing in Beringia during this time, then the concept of a standstill there is also questionable.

While genetic data could suggest that a population standstill occurred, the exact location remains uncertain.

 

It could have happened in places like Kamchatka, the Kuril Islands, Sakhalin Island, coastal areas of Alaska, or even elsewhere in Eurasia.

 

In fact, evidence from archaeology and genetics suggests that the hunter-gatherer populations in northern Siberia likely retreated as conditions became colder and drier during the peak of the Ice Age, meaning Beringia may not have hosted a stable population.

 

Most of the last glacial period saw the western part of Beringia unoccupied, leading to doubts about the survival of a small group of people in central or eastern Beringia while populations in similar environments to the west moved south.

 

Some paleoenvironmental studies suggest that certain habitats in Beringia could have supported human life during the Last Glacial Maximum, but contrary data about the region's fauna indicates that the area was largely inhospitable for human settlement during this period.

 

For instance, research found that evidence of human interaction with Beringian bison only appears well after the last glacial period.

 

As the Last Glacial Maximum came to an end, around 19,000 to 15,000 years ago, temperatures began to rise, and the ice started to retreat. Sea levels also rose gradually as the ice melted.

 By 14,000 years ago, the ice sheets had shrunk enough to create a narrow corridor between them, but it likely wasn't passable by humans until around 13,500 years ago years ago due to the presence of large proglacial lakes.

Additionally, the area may not have been biologically productive enough to support human life until around 12,000 years ago.

While the inland route was blocked, a coastal path from Beringia was likely only closed between 18,000 and 15,000 years ago. Along this coast, there were pockets of survivable land, which could have enabled people to move by boat.

The rapid climate warming between 15,000 and 14,000 years ago melted the ice sheets, raising sea levels and flooding coastal areas.

The date of around 14,500 years ago is key for determining whether humans first colonized the Americas during the last glacial period or after, as conditions before and after this time were vastly different.

The widely accepted theory is that the first people in the Americas crossed the Bering land bridge from Asia during the Ice Age.

This belief is deeply rooted in both archaeology and genetics, with many studies assuming this migration route without much questioning. However, the actual evidence supporting this theory is surprisingly limited.

 

Scientific papers regularly repeat the idea that the Bering land bridge was the entry point for humans into the Americas during the late Pleistocene (around 15,000 years ago or earlier).

 

This is accepted almost without question, even though direct evidence for this migration is sparse.

 If there was a population in Beringia (the area between Siberia and Alaska), we don’t have much evidence of them today, partly because much of that land is now submerged underwater.

As archaeologist noted, while we assume that the first Americans came from northeast Asia, finding proof of their presence in Beringia has been challenging.

 

The distances between the Altai Mountains (believed to be a key region of origin for Native Americans) and both the Pacific coast of Beringia and the Atlantic coast of Norway are nearly identical.

This raises the possibility that there could have been multiple entry points into the Americas, perhaps via both the west (through Beringia) and the east (via an Atlantic route).

Three main hypotheses propose multiple entry points for the first Americans. The Ice-Free Corridor Model suggests big-game hunters crossed the Bering land bridge and moved south via an ice-free passage between retreating ice sheets.

The Solutrean Hypothesis posits that European foragers navigated the North Atlantic ice margins, reaching North America during the Last Glacial Maximum.

 The Pacific Coastal Hypothesis suggests seafaring foragers entered along the Pacific coast and spread southward. Currently, insufficient evidence supports any single theory, and further research is needed to clarify early migration routes.

The Ice-free corridor model has long been the dominant theory for the initial peopling of the Americas, positing that Siberian foragers entered North America around 14,000 years ago through a narrow corridor between retreating ice sheets.

These foragers, equipped with Clovis-style bifaces for hunting megafauna, supposedly spread rapidly across the continent, leading to the extinction of many Pleistocene species. This model is understood in relation Clovis First model, and has been supported by several empirical data sets.

 These included the presence of Clovis-like technology in the vicinity of the corridor, the opening of the corridor before Clovis sites appeared, a trend in the north-to-south distribution of Clovis sites, and evidence suggesting Clovis hunters were responsible for the extinction of some megafauna.

However, critical assessments reveal significant gaps. First, the claims that there were foraging populations in Beringia prior to the corridor's opening, lacks supporting evidence.

Second, the dating of the corridor remains debated, with estimates suggesting it may have opened anytime between 14.5 and 10.5 thousand years ago.

If we accept an opening around 14,000 years ago, Clovis hunters could have reached northern Mexico by 13,500 years ago, contingent on the corridor's ecosystems being conducive to human habitation.

 Third, the conclusions depend on the acceptance of either a “long” or “short” Clovis chronology, complicating the interpretation of age trends among Clovis sites. Fourth, there is contentious debate on whether Clovis hunters caused megafauna extinction, climate change was responsible, or if a combination of factors was at play.

Moreover, the hypothesis that the rapid spread of Clovis hunters was due to their specialization in hunting large mammals is further called into question.

 The close timing of large mammal extinctions has often been used to support the theory of a swift human dispersal, but evidence suggests that not all extinct species vanished around the same time.

 In fact, only about half of the known genera went extinct after 14,000 years ago, and some survived into the Clovis period.

 Finally, the question of human occupation in the Americas prior to Clovis remains crucial, as the evidence for such early human presence could challenge the validity of the ice-free corridor model altogether.

The Solutrean Hypothesis suggests that early humans from Europe, known for their Solutrean stone tools, might have traveled to North America by crossing ice shelves in the North Atlantic during the Ice Age.

This idea is based on the similarities between Solutrean tools and Clovis tools found in North America, hinting at a possible link through shared ancestry or similar development. However, this theory lacks solid evidence and hasn’t been thoroughly tested, making it questionable.

Some evidence, like marine shells and seal bones found in caves in Spain, suggests Solutrean people used coastal resources. But critics say they mostly relied on land-based resources, and shifting coastlines over time make it hard to interpret.

The theory also relies on the idea that there were ice shelves in the North Atlantic, which could have allowed for seal hunting, but some studies argue that warmer seas would have made these ice shelves rare.

Overall, there’s little direct proof for this model. The age of archaeological sites in eastern North America that are thought to be very old (17,000 to 20,000 years) doesn’t directly support this theory, just extends the timeline.

The biggest argument for the hypothesis is the similarity in tools between the two regions, but this could have been independent invention. Without stronger evidence, like DNA links or Solutrean-style tools found in North America, this hypothesis remains speculative and unproven.

The Pacific coast model, suggests that human foragers colonized the Americas by navigating the northern Pacific coastline, moving between islands and refugia before dispersing along the coast from Beringia.

While this hypothesis aligns with the timing of the last glacial interval, it has faced challenges due to the lack of substantial evidence and a clear chronology, especially considering the inundation of many potential habitation sites by post-glacial sea-level rise.

Support for the Pacific coast model comes from various data, including evidence of Upper Paleolithic foragers using boats in the Japanese archipelago at least 30,000 years ago. However, the extent of coastal adaptation along the Kuril Islands and the Kamchatka Peninsula remains unclear. Additionally, some modern Siberian populations share genetic markers with Native American groups, suggesting a potential connection, although there is no direct evidence of these populations existing during the Last Glacial Maximum . While there are indications of refugia along the northeastern Pacific coast and evidence of coastal resource use around 13,000 to 11,000 years ago, key archaeological sites like Monte Verde and Huaca Prieta is primarily the basis for earlier coastal adaptations.

A variant of this model posits that the use of stemmed points by coastal populations indicates a lineage between Japanese Upper Paleolithic cultures and those in North America. However, like the Solutrean hypothesis, this raises the issue of whether these similarities stem from convergent evolution or direct descent. The model is somewhat bolstered by genetic evidence linking early burials in the Americas to coastal populations, yet it also faces competing theories suggesting multiple migration routes, including an ice-free corridor or Arctic coastal paths.

In conclusion, while each model regarding the initial peopling of the Americas—whether the Atlantic ice shelf model, the Pacific coast model, or the ice-free corridor model—has its proponents, none can be completely dismissed or fully validated at this stage.

 

After Reaching Americas, the Ancestral Native American lineage experienced internal splits, with the 'Big Bar' lineage branching off around 21,000-16,000 years ago. Another split occurred around 15.7 thousand years ago, resulting in Northern Native American (NNA) and Southern Native American populations. The Big Bar lineage moved south from eastern Beringia (Alaska), and the NNA–SNA split likely occurred farther south, supported by genetic evidence showing equidistance to Ancient Beringian individuals.

 

 

Ancestral Native American individuals likely crossed Beringia and reached North America south of the continental ice sheets before Ancient Beringian individuals. The dispersal patterns of Northern Native Americans and Southern Native American populations differed. Northern Native Americans remained in northern North America, eventually shifting northward in the Holocene. Southern Native American populations rapidly spread southward, showing close genetic links between ancient individuals in North and South America. There were at least two late Pleistocene pulses of Southern Native American groups into South America.

 

The genetic history of dogs parallels the human peopling process, suggesting domestication in Siberia or Beringia.

 

Scientists have studied the DNA of many ancient and modern dogs. The analysis of nuclear DNA shows that all dogs come from three main groups of ancestors, one from Western Eurasia, one from East Asia (like dingoes), and one from the Arctic (like huskies and ancient American dogs). These lineages were established at least 11,000 years ago.

When looking at mitochondrial DNA, most modern dogs fall into four main groups called haplogroups A, B, C, and D. The majority belong to haplogroup A. Ancient DNA studies found a unique haplogroup A2B in pre-contact dogs in the Americas south of the Arctic, but it has almost disappeared in modern dogs.

Within A2 B, there are four subgroups A2 B1 to A2 B4, while A2 B1 is found all across the Americas, the others are more localized.

Scientists used molecular clock analysis to estimate when these haplogroups split. The oldest split within haplogroup A is estimated to be around 22,800 years ago. This suggests that dogs were domesticated several thousand years before they appeared in the archaeological record. This early timeline suggests that dogs were likely domesticated by the time humans migrated into the Americas.

The relationship between the migration of humans and dogs into the Americas during the late Pleistocene period is fascinating. It suggests that dogs may have accompanied the first people entering the Americas and explores the timeline of their divergence.

The Americas were settled by humans relatively late, and it's possible that when people first arrived, they had dogs with them. Dogs could have played a role in helping humans quickly spread throughout the region. Comparing the timelines of dog and human populations, researchers found key points of convergence.

The introduction of dogs in the Americas is estimated using mitochondrial data, and it aligns with the timing of human population splits. Ancient American dogs, excluding the Arctic, belong to the same lineage, suggesting they coalesced with a Siberian dog lineage around sixteen thousand four hundred years ago. This timeframe coincides with the peopling of the Americas.

The evidence indicates that dogs likely crossed the Beringia land bridge during the Pleistocene, reaching the Americas before later human migrations. The split between major Native American lineages aligns with the divergence of dog lineages, suggesting they evolved together.

While both Ancestral Native Americans and Ancient Beringians groups could have brought dogs into the Americas, archaeological evidence hints that Ancestral Native Americans might have been the first, arriving before the distinctive Ancient Beringians group. This suggests a connection between the migration of people and dogs into the Americas during this period.

Ancient DNA suggests that dog domestication likely began in Siberia during the Late Pleistocene, a period around twenty six to nineteen thousand seven hundred years ago. This aligns with the time when humans and their genetically divergent groups were present in Siberia and western Beringia. The evidence indicates that human populations in this region were small and lived in relative isolation.

The lack of significant gene flow among these groups and the absence of archaeological sites suggest limited interaction with communities outside Siberia. As these populations, specifically the ancestors of Native Americans, crossed into the Americas, they brought dogs with them. The question arises: How did Ancestral Native Americans acquire dogs? The researchers propose that dogs were likely domesticated from a wolf population in Siberia or western Beringia during the Late Pleistocene before Ancestral Native Americans migrated into the Americas.

Among the various groups present in Siberia during the Last Glacial Maximum, the researchers eliminate some possibilities and suggest that the Ancient North Siberians are the more likely population to have initiated the domestication process. Genomic analyses of Ancestral North Siberians individuals at Siberian sites show evidence of gene flow into both ancient Native American and Western Eurasian lineages.

This suggests a mechanism for the transfer of dogs into different groups, supporting their movement both east and west following domestication. The researchers propose that climatic conditions during the Last Glacial Maximum brought human and wolf populations into proximity within refugial areas, leading to increased interactions. Mutual scavenging of kills or wolves drawn to human campsites may have initiated a shift in the relationship between humans and wolves, eventually resulting in dog domestication.

 

No genomic evidence supports the controversial claim that the first peoples came from Europe via the North Atlantic. Claims about 'Palaeoamericans' having different ancestry, possibly related to European or other populations, have been rejected. All ancient human genomes from the Americas, except for later arriving Palaeo-Inuit and Inuit Thule groups, show closer affinities to contemporary Native American peoples than to any other present-day populations worldwide.

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During the Holocene, human migration continued between northeast Asia, the Bering Strait, and the Americas. The earliest evidence of Bering Strait crossings is seen in the Ocean Bay tradition around 5,200 years ago. Athabaskan groups in northern North America show East Asian genetic ancestry from gene flow around 5,000–4,400 years ago, likely from ‘proto-Palaeo-Eskimos.’ The North American Arctic saw two major cultural traditions: the Palaeo-Inuit (~5,200 years ago to AD 1500) and the Thule culture (ancestors of today’s Inuit), spreading around AD 200. There’s evidence of back migration from the Americas to Siberia.

In the Americas, ancient populations rapidly expanded but remained largely settled after initial migrations. Groups like the Clovis and Fishtail cultures, which appeared after 13,500 years ago, spread widely across the continents. Despite challenging conditions, many populations persisted in isolation, such as the Ancient Beringians who left no modern descendants. The Andes and islands like British Columbia show genomic differences caused by both geographic and social isolation. In the Caribbean and Mesoamerica, gene flow occurred, particularly during the expansion of the Inca Empire. Polynesian and Native American contact in the eastern Pacific around the 13th century suggests interactions between these distant populations.

There is no substantial evidence supporting the existence of a Beringian population that remained isolated during the Last Glacial Maximum, only to rapidly expand into the Americas as conditions improved. While there is genetic evidence for a population bottleneck, the specifics regarding its location, cause, and mechanisms are speculative at best. Archaeological and genetic data indicate that the foraging populations in northern Siberia likely retreated southward and abandoned at least the western part of Beringia during the harsh conditions of the Last Glacial Maximum , challenging the narrative of a stable, isolated population waiting to spread into the Americas.