How did people realize that America was a different continent?

American schools teach that the American continents are named after Amerigo Vespucci because he realized that Columbus had not sailed to Asia but rather a new continent. If this story is true, how did Amerigo realize this? If not, who was first to realize America was a different continent, and what was the evidence for this?

Columbus and everybody else at the time believed that he had discovered the Eastern shores of Asia. Vespucci was one of those amongst the everybody else. An essay by Jonathan Cohen titled, The Naming of America: Fragments we've shored against ourselves, covers the naming of America in some detail. In it, Cohen notes:

The voyage completed by Vespucci between May 1499 and June 1500 as navigator of an expedition of four ships sent from Spain under the command of Alonso de Hojeda is certainly authentic. This is the second expedition of the traditional series. Since Vespucci took part as navigator, he certainly cannot have been inexperienced; however, it seems unlikely that he had made a previous voyage, though this matter remains unresolved. In the voyage of 1499-1500, Vespucci would seem to have left Hojeda after reaching the coast of what is now Guyana (Carew's homeland). Turning south, he is believed to have discovered the mouth of the Amazon River and explored the coast of present-day Brazil. On the way back, he reached Trinidad, sighting en route the mouth of the Orinoco River, and then made for Haiti. Vespucci thought he had sailed along the coast of the extreme easterly peninsula of Asia, where Ptolemy, the 2nd-century Greek geographer, believed the market of Cattigara to be; so he looked for the tip of this peninsula, calling it Cape Cattigara. He supposed that the ships, once past this point, emerged into the seas of southern Asia. As soon as he was back in Spain, he equipped a fresh expedition with the aim of reaching Asia. But the Spanish government did not welcome his proposals, and at the end of 1500 Vespucci went into the service of Portugal.

Under Portuguese auspices he completed a second expedition, which set sail from Lisbon on May 31, 1501. After a halt at the Cape Verde Islands, the expedition traveled southwestward, reached the coast of Brazil, and certainly sailed as far south as the Río de la Plata, which Vespucci was the first European to discover. In all likelihood the ships took a quick run still farther south, along the coast of Patagonia to the Golfo de San Juli n or beyond. His ships returned by an unknown route, anchoring at Lisbon on July 12, 1502. This voyage is of fundamental importance in the history of geography in that Vespucci himself became convinced that the lands he had explored were not part of Asia but a New World. Unlike Columbus, who, to his death, clung to the idea that he had found the shores of Asia, Vespucci defined what had indeed been found - and for this he has been rightfully honored.

Much of this information has been gleaned from Vespucci's letters to his sponsors (also published as Mundus Novus, i.e., New World) where he provides the how he knew that it was not Asia and was instead a new continent that he had discovered:

For the opinion of the ancients was, that the greater part of the world beyond the equinoctial line to the south was not land, but only sea, which they have called the Atlantic; and if they have affirmed that any continent is there, they have given many reasons for denying that it is inhabited. But this their opinion is false, and entirely opposed to the truth. My last voyage has proved it, for I have found a continent in that southern part; more populous and more full of animals than our Europe, or Asia, or Africa, and even more temperate and pleasant than any other region known to us, as will be explained further on.

It was on the 7th of August 1501, that we reached those countries, thanking our Lord God with solemn prayers, and celebrating a choral Mass. We knew that land to be a continent, and not an island, from its long beaches extending without trending round, the infinite number of inhabitants, the numerous tribes and peoples, the numerous kinds of wild animals unknown in our country, and many others never seen before by us, touching which it would take long to make reference.

In other words, Vespucci concluded that he had discovered a continent based on the following facts:

  • huge land mass
  • extending further south than Asia
  • different flora and fauna
  • different peoples

A resulting map from 1507 which is often credited as the source for the name America looked like this:

coleopterist has made a good answer, but I will add a few details that are less obvious and not easy to glean from the literature.

First of all, the fiction that Columbus had discovered the Indies was maintained for quite long time, up to about 1520 when it became patently obvious that the two places were different. This fiction was maintained not because people were fooled by it, but because it was politically expedient. As long as people thought that Spain had reached the spice-rich Indies, it was beneficial to the crown.

In truth, among experts and experienced navigators it was well known secretely almost immediately that Columbus had found some new place because it was known that the Arabs were widespread in Southeast Asia and these people were not present in the new world.

After the first voyage of Columbus there was some question, because there was the possibility he had somehow found some remote, outlying islands of the Indies. However, when ships from Columbus' massive second expedition began returning in 1495 and 1496 it rapidly became clear to experts that it was a new place because the inhabitants were much more primitive than India was known to be and there were no Arabs there or any other ships (such as those from China) at all for that matter. Since there were no Indian, Chinese or Arab ships anywhere and the people were all naked savages with no knowledge of bronze or other technology, it was clear it was a new place.

The first people who populated the Americas

Many thousands of years ago, not a single human being lived in the Americas.

This only changed during the last Ice Age. It was a time when most of North America was covered with a thick sheet of ice, which made the Americas difficult to inhabit.

But at some point during this time, adventurous humans started their journey into a new world.

They probably came on foot from Siberia across the Bering Land Bridge, which existed between Alaska and Eurasia from the end of the last Ice Age until about 10,000 years ago. The area is now submerged by water.

There is still debate about when these first Americans actually arrived and where they came from. But we are now getting closer to uncovering the original narrative, and finding out who these first Americans really were.

During the peak of the last Ice Age about 20,000 years ago, a journey from Asia into the Americas would not have been particularly desirable. North America was covered in icy permafrost and tall glaciers. But, paradoxically, the presence of so much ice meant that the journey was, in a way, easier than it would be today.

The abundance of ice meant that sea levels were much lower than they are now, and a stretch of land emerged between Siberia and Alaska. Humans and animals could simply walk from Asia to North America. The land bridge was called Beringia.

People were using the woody shrubs from the land bridge to ignite bones on the landscape

At some point around this time &ndash known as the Last Glacial Maximum &ndash groups of hunter-gatherers moved east from what is now Siberia to set up camp there.

"The first people who arrived in Beringia were probably small, highly mobile groups evolving in a large landscape, probably depending on the availability of seasonal resources," says Lauriane Bourgeon of the University of Montreal, Canada.

These people did well to seek refuge there. Central Beringia was a much more desirable environment than the icy lands they had left behind. The climate was a bit damper. Vegetation, in the form of woody shrubs, would have given them access to wood that they could burn to keep warm.

Beringia was also an ideal environment for large grazing mammals, giving early hunter-gathers something to hunt, says Scott Elias of Royal Holloway, University London in the UK, who reconstructs past climates.

"Our hypothesis is that people were using the woody shrubs from the land bridge to ignite bones on the landscape. The bones of big animals contain lots of fatty deposits of marrow, and they will burn."

When humans got to Beringia, they would have had little choice but to set up camp there. The vast Laurentide and Cordilleran ice sheets further east cut them off from North America.

This standstill helped these isolated groups of people to become genetically distinct from those they had left behind

It is now becoming clear that they made Beringia their home, staying put for several thousand years. This idea is called the Beringian Standstill Hypothesis. This standstill helped these isolated groups of people to become genetically distinct from those they had left behind, according to a 2007 study.

This long standstill therefore meant that the people who arrived in the Americas &ndash when the ice finally retreated and allowed entry &ndash were genetically different to the individuals who had left Siberia thousands of years earlier. "Arguably one of the most important parts of the process is what happened in Beringia. That's when they differentiated from Asians and started becoming Native Americans," says Connie Mulligan of the University of Florida in Gainesville, US, who took part in this early analysis.

Since then, other genetic insights have further supported the standstill hypothesis. Elias and colleagues even propose that people stayed in Beringia for as long as 10,000 years.

When the ice finally started to retreat, groups of people then travelled to different pockets of the Americas.

There has long been debate over whether these early settlers arrived from several migrations from different areas, or just one.

There's been no turnover or change in the population group as some people had previously hypothesised

Over 20 years ago, Mulligan proposed that there was just one migration from Beringia into the "New World". She came to this conclusion by analysing the genetic variation in the DNA of modern-day Native Americans and comparing it with the variation in Asia. The same rare pattern appeared in all the Native Americans she studied, but very rarely appeared in modern-day Asians. This meant Native Americans likely arose from a single population of people who had lived in Beringia, isolated for many years.

In 2015, a study using more advanced genetic techniques came to a similar conclusion. Rasmus Nielsen of the University of California, Berkeley, US, and colleagues found that the "vast majority" of Native Americans must have originated from just one colonisation event.

"There's been no turnover or change in the population group as some people had previously hypothesised," says Nielsen. In fact, about 80% of Native Americans today are direct descendants of the Clovis people, who lived across North America about 13,000 years ago. This discovery came from a 2014 genetic study of a one-year-old Clovis boy who died about 12,700 years ago.

But we now know there must have been staggered migrations from Beringia.

That is because there are small groups of people in the Amazonian region of South America &ndash such as the Suruí and Karitiana &ndash with additional mysterious "arctic gene flow", unrelated to the Clovis boy. Another 2015 study therefore proposed there was more than one "founding population of the Americas".

The indigenous populations of the Americas, the team found, have distant genetic links in common with people of Australia, Papua New Guinea and the Andaman Islands.

People came into Beringia over different times during the standstill

This means, says Pontus Skoglund of Harvard University in Boston, Massachusetts, that people came into Beringia over different times during the "standstill" and went on to populate different parts of the Americas. Those early dispersals are still reflected by differences in the genomes of people living today.

"It wasn't simply a single homogenous founding population. There must have been some type of patchwork of people, and maybe there were multiple pulses," says Skoglund.

In other words, the Beringian inhabitants did not all arrive or leave at the same time.

This makes sense when you consider that Beringia was not a narrow land bridge with ocean on either side. "It was a huge region about twice the size of Texas," says Elias. The people living there would have had no idea that it was a land bridge at all. "There were no sign posts saying they were leaving Siberia."

This makes it highly likely that there were different groups of Beringian inhabitants that never met.

A study published in February 2017 strengthens this idea further. After examining the shapes of 800- to 500-year-old skulls from Mexico, researchers found they were so distinct, the people the skulls belonged to must have remained genetically isolated for at least 20,000 years.

To understand who the first Americans really were, we have to consider when they arrived. While the exact timing is hard to pin down. Nielsen's work gives some insight. By sequencing the genomes of people from the Americas, Siberia, and Oceania, he and colleagues could understand when these populations diverged. The team concludes that the ancestors of the first Americans came to Beringia at some point between 23,000 years and 13,000 years ago.

We found cut marks on bones from horse, caribou and wapiti so we know that humans were relying on those species

We now have archaeological evidence to suggest that the people who left Siberia &ndash and then Beringia &ndash did so even earlier than the 23,000-year-limit proposed by Nielsen and colleagues. In January 2017, Lauriane Bourgeon and her team found evidence of people living in a cave system in the northern Yukon Territory of western Canada, called the Bluefish Caves, that dates to as early as 24,000 years ago. It was previously believed that people had only arrived in this area 10,000 years later.

"They reached Beringia as early as 24,000 years ago, and they remained genetically and geographically isolated until about 16-15,000 years ago, before dispersing south of the ice sheets that covered most of North America during this period," says Bourgeon.

The caves "were only used on brief occasions for hunting activities", she says. "We found cut marks on bones from horse, caribou and wapiti, so we know that humans were relying on those species."

This work provides further evidence that people were in the Beringia area at this early date. But it does not reveal the exact dates these people first ventured further south.

For that, we can turn to archaeological evidence. For decades, stone tools left by the Clovis people have been found throughout North America. Some date to as early as 13,000 years ago. This might suggest that humans moved south very late. But in recent years evidence has begun to emerge that questions this idea.

Most preserved remains are stone tools and sometimes bones of animals

For instance, at a site called Monte Verde in southern Chile, there is evidence of human occupation that dates between 14,500 and 18,500 years ago. We know these people built fires, ate seafood and used stone tools &ndash but because they did not leave any human remains behind, much about this early group remains mysterious.

"We really know little about them, because most preserved remains are stone tools and sometimes bones of animals, thus technology and diet," explains Tom Dillehay of Vanderbilt University in Tennessee, US, who is studying these people. "Monte Verde in south-central Chile, where I am at present, has several organic remains &ndash animal hide, meat, plant remains that reveal a wider diet, wood technology &ndash but these types of sites are rare to find."

Another conundrum remains. Ice sheets still covered North America 18,500 years ago, making journeying south difficult. How did people arrive in southern Chile so early?

A leading idea had been that an ice-free corridor opened up, which allowed humans to travel south. However, the latest evidence suggests this corridor only opened about 12,600 years ago, long after these early Chileans arrived.

Elias also points out how difficult this journey would have been. "Even if there was a small gap in between these enormous ice sheets, the environment left in that gap would have been so horrible, with mud, ice, meltwater and slush. It would not have been a habitable place for people or the animals they would have wanted to follow," he says.

These early people could have travelled by boat

There is an alternative. These early people could have travelled by boat, taking a route along the Pacific coast. There is no archaeological evidence to support this idea, but that is not entirely unexpected: wooden boats are rarely preserved in the archaeological record.

There are still many unanswered questions, but Mulligan says that studying how and when early hunter-gatherers spread across the Americas can help us to understand the process of migration itself. That is, how population sizes change and which genetic traits persist.

In many ways, the peopling of America presents scientists with a golden opportunity to study these processes. There have been multiple migrations both into and out of other regions of the world &ndash Africa, Europe and Asia, for instance. But the people who moved into the Americas were on a one-way journey. "We know the original inhabitants came from Asia into the New World with no other people there, and no major back migrations, so it's the simplest model you can conceive of."

That it was a one-way journey, coupled with the increased interest in studying the genetics of these ancient people, means we should soon understand even more about who these first Americans really were, and exactly when they arrived.

Melissa Hogenboom is BBC Earth's associate editor. She is @melissasuzanneh on Twitter.

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The North American Indian heritage

The date of the arrival in North America of the initial wave of peoples from whom the American Indians (or Native Americans) emerged is still a matter of considerable uncertainty. According to prevailing thought, it is relatively certain that they were Asiatic peoples who originated in northeastern Siberia and crossed the Bering Strait (perhaps when it was a land bridge) into Alaska and then gradually dispersed throughout the Americas. The glaciations of the Pleistocene Epoch (about 1,800,000 to 11,700 years ago) coincided with the evolution of modern humans, and ice sheets blocked ingress into North America for extended periods of time. It was only during the interglacial periods that people ventured into this unpopulated land. Some scholars claim an arrival about 60,000 years ago, before the last glacial advance (Wisconsin Glacial Stage). The latest possible date now seems to be about 20,000 years ago, with some pioneers filtering in during a recession in the Wisconsin glaciation.

These prehistoric invaders were Stone Age hunters who led a nomadic life, a pattern that many retained until the coming of Europeans. As they worked their way southward from a narrow, ice-free corridor in what is now the state of Alaska into the broad expanse of the continent—between what are now Florida and California—the various communities tended to fan out and to hunt and forage in comparative isolation. Until they converged in the narrows of southern Mexico and the confined spaces of Central America, there was little of the fierce competition or the close interaction among groups that might have stimulated cultural inventiveness. Although great architectural and scientific advances did occur in Mesoamerica, there was markedly less in the way of metallurgy, transportation networks, and complex commerce than among the contemporary civilizations of Asia, Europe, and sections of Africa. Cities appeared first among the Olmec in the strategic narrows between Mexico and Central America and among the Maya in portions of Guatemala, the Yucatán Peninsula, and Honduras. Subsequently, the Toltec and Aztec created some remarkable cities in the high Mexican Plateau and developed a society whose crafts and general sophistication rivaled those of Europe. These dense populations were based on a productive agriculture that relied heavily on corn (maize), beans, and squash, along with a great variety of other vegetables and fruits, fibres, dyes, and stimulants but almost no livestock.

The size of the pre-Columbian aboriginal population of North America remains uncertain, since the widely divergent estimates have been based on inadequate data. Luis de Velasco, a 16th-century viceroy of New Spain (Mexico), put the total for the West Indies, Mexico, and Central America at about 5,000,000 some modern scholars, however, have suggested a figure two to five times larger for the year 1492. The pre-Columbian population of what is now the United States and Canada, with its more widely scattered societies, has been variously estimated at somewhere between 600,000 and 2,000,000. By that time, the Indians there had not yet adopted intensive agriculture or an urban way of life, although the cultivation of corn, beans, and squash supplemented hunting and fishing throughout the Mississippi and Ohio river valleys and in the Great Lakes–St. Lawrence River region, as well as along the Gulf of Mexico and Atlantic Coastal Plain. In those areas, semisedentary peoples had established villages, and, among the Iroquois and the Cherokee, powerful federations of tribes had been formed. Elsewhere, however, on the Great Plains, the Canadian Shield, the northern Appalachians, the Cordilleras, the Great Basin, and the Pacific Coast, hunting, fishing, and gathering constituted the basic economic activity and, in most instances, extensive territories were needed to feed and support small groups.

The history of the entire aboriginal population of North America after the Spanish conquest has been one of unmitigated tragedy. The combination of susceptibility to Old World diseases, loss of land, and the disruption of cultural and economic patterns caused a drastic reduction in numbers—indeed, the extinction of many communities. It is only since about 1900 that the numbers of some Native American peoples have begun to rebound.

Finding Ways

As scientists debate the peopling of the Americas, it’s worth noting there could be more than one right answer. “I think current evidence indicates multiple migrations, multiple routes, multiple time periods,” says Torben Rick, an anthropologist at Smithsonian’s National Museum of Natural History.

Rick began his own career studying a likely migration along the “Kelp Highway”—the rim of coastline that apparently once stretched from Asia all the way around to North America.

“People could basically stair-step their way around the coast and have a similar suite of resources that they were in general familiar with,” says Rick, who has spent years excavating sites on the California coast. Rick’s late Smithsonian colleague Dennis Stanford famously advocated the Solutrean hypothesis, which claims the first Americans came over from Europe, crossing the ice of the North Atlantic. Rick isn’t sold on the idea, but he praises Stanford’s willingness to explore an unusual notion: “If we don’t look and we don’t test it and don’t rigorously go after it, we’ll never know for sure.”

Regarding sites in South America that date back more than 14,000 years, could humans have traveled there by boat, perhaps from Oceania? It’s a question
researchers have had to consider. But, Rick says, the theory “doesn’t pass the smell test” because it’s unlikely that people then were capable of crossing an open ocean.

Still, he notes that scientists don’t know much about prehistoric watercraft because they were made of perishable materials. “We can say, ‘Ha-ha, that idea doesn’t work’—but I can’t tell you exactly why those early sites are there,” he admits. “Human ingenuity is incredible. I would never underestimate it.”

6 The Indians Weren't Defeated by White Settlers

Our history books don't really go into a ton of detail about how the Indians became an endangered species. Some warring, some smallpox blankets and . death by broken heart?

When American Indians show up in movies made by conscientious white people like Oliver Stone, they usually lament having their land taken from them. The implication is that Native Americans died off like a species of tree-burrowing owl that couldn't hack it once their natural habitat was paved over.

But if we had to put the whole Cowboys and Indians battle in a Hollywood log line, we'd say the Indians put up a good fight, but were no match for the white man's superior technology. As surely as scissors cuts paper and rock smashes scissors, gun beats arrow. That's just how it works.

There's a pretty important detail our movies and textbooks left out of the handoff from Native Americans to white European settlers: It begins in the immediate aftermath of a full-blown apocalypse. In the decades between Columbus' discovery of America and the Mayflower landing at Plymouth Rock, the most devastating plague in human history raced up the East Coast of America. Just two years before the pilgrims started the tape recorder on New England's written history, the plague wiped out about 96 percent of the Indians in Massachusetts.

In the years before the plague turned America into The Stand, a sailor named Giovanni da Verrazzano sailed up the East Coast and described it as "densely populated" and so "smoky with Indian bonfires" that you could smell them burning hundreds of miles out at sea. Using your history books to understand what America was like in the 100 years after Columbus landed there is like trying to understand what modern day Manhattan is like based on the post-apocalyptic scenes from I Am Legend.

Historians estimate that before the plague, America's population was anywhere between 20 and 100 million (Europe's at the time was 70 million). The plague would eventually sweep West, killing at least 90 percent of the native population. For comparison's sake, the Black Plague killed off between 30 and 60 percent of Europe's population.

While this all might seem like some heavy shit to lay on a bunch of second graders, your high school and college history books weren't exactly in a hurry to tell you the full story. Which is strange, because many historians believe it is the single most important event in American history. But it's just more fun to believe that your ancestors won the land by being the superior culture.

European settlers had a hard enough time defeating the Mad Max-style stragglers of the once huge Native American population, even with superior technology. You have to assume that the Native Americans at full strength would have made shit powerfully real for any pale faces trying to settle the country they had already settled. Of course, we don't really need to assume anything about how real the American Indians kept it, thanks to the many people who came before the pilgrims. For instance, if you liked playing cowboys and Indians as a kid, you should know that you could have been playing vikings and Indians, because that shit actually happened. But before we get to how they kicked Viking ass, you probably need to know that .

Related: 5 Ridiculous Myths Everyone Believes About the Wild West

Continental drift

Continental drift describes one of the earliest ways geologists thought continents moved over time. Today, the theory of continental drift has been replaced by the science of plate tectonics.

Earth Science, Geology, Geography, Physical Geography

Colliding Skyward
The collision of the Indian subcontinent and Asian continent created the Himalayan mountain range, home to the world's highest mountain peaks, including 30 that exceed 7300 meters (24,000 feet). Because continental drift is still pushing India into Asia, the Himalayas are still growing.

to adjust to new surroundings or a new situation.

(1880-1930) German meteorologist and geologist.

a group of closely scattered islands in a large body of water.

region at Earth's extreme north, encompassed by the Arctic Circle.

person who studies space and the universe beyond Earth's atmosphere.

all weather conditions for a given location over a period of time.

edge of land along the sea or other large body of water.

one of the seven main land masses on Earth.

the movement of continents resulting from the motion of tectonic plates.

always changing or in motion.

remnant, impression, or trace of an ancient organism.

having to do with a habitat or ecosystem of a lake, river, or spring.

person who studies the physical formations of the Earth.

study of the physical history of the Earth, its composition, its structure, and the processes that form and change it.

series of faults and other sites of tectonic activity stretching from southwestern Asia to the Horn of Africa.

environment where an organism lives throughout the year or for shorter periods of time.

strong or able to withstand severe weather.

air containing a large amount of water vapor.

interlocking pieces that, when correctly put together, display a picture or design.

process or assembly that performs a function.

freshwater reptile that lived during the early Permian period, about 300 million years ago.

underwater mountain range that runs from Iceland to Antarctica.

underwater mountain range.

solid material turned to liquid by heat.

series or chain of mountains that are close together.

thin layer of the Earth that sits beneath ocean basins.

supercontinent of all the Earth's landmass that existed about 250 million years ago.

movement and interaction of the Earth's plates.

animal that breathes air and usually has scales.

depression in the ground caused by the Earth's crust spreading apart.

object's complete turn around its own axis.

rift in underwater mountain range where new oceanic crust is formed.

flat, thick piece of material such as earth or stone.

individual organism that is a typical example of its classification.

study of rock layers and layering.

process of one tectonic plate melting, sliding, or falling beneath another.

ancient, giant landmass that split apart to form all the continents we know today.

massive slab of solid rock made up of Earth's lithosphere (crust and upper mantle). Also called lithospheric plate.

existing in the tropics, the latitudes between the Tropic of Cancer in the north and the Tropic of Capricorn in the south.

climate group that experiences hot, wet summers.

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Caryl-Sue, National Geographic Society

Last Updated

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Related Resources

Plate Tectonics

The Earth&rsquos surface may seem motionless most of the time, but it&rsquos actually always moving, ever so slowly, at a scale that is difficult for humans to perceive. The Earth&rsquos crust is broken up into a series of massive sections called plates. These tectonic plates rest upon the convecting mantle, which causes them to move. The movements of these plates can account for noticeable geologic events such as earthquakes, volcanic eruptions, and more subtle yet sublime events, like the building of mountains. Teach your students about plate tectonics using these classroom resources.

Continental Drift versus Plate Tectonics

A scientific idea that was initially ridiculed paved the way for the theory of plate tectonics, which explains how Earth&rsquos continents move.

Plate Tectonics

The theory of plate tectonics revolutionized the earth sciences by explaining how the movement of geologic plates causes mountain building, volcanoes, and earthquakes.


A continent is one of Earth&rsquos seven main divisions of land. The continents are, from largest to smallest: Asia, Africa, North America, South America, Antarctica, Europe, and Australia.

Related Resources

Plate Tectonics

The Earth&rsquos surface may seem motionless most of the time, but it&rsquos actually always moving, ever so slowly, at a scale that is difficult for humans to perceive. The Earth&rsquos crust is broken up into a series of massive sections called plates. These tectonic plates rest upon the convecting mantle, which causes them to move. The movements of these plates can account for noticeable geologic events such as earthquakes, volcanic eruptions, and more subtle yet sublime events, like the building of mountains. Teach your students about plate tectonics using these classroom resources.

Continental Drift versus Plate Tectonics

A scientific idea that was initially ridiculed paved the way for the theory of plate tectonics, which explains how Earth&rsquos continents move.

Plate Tectonics

The theory of plate tectonics revolutionized the earth sciences by explaining how the movement of geologic plates causes mountain building, volcanoes, and earthquakes.


A continent is one of Earth&rsquos seven main divisions of land. The continents are, from largest to smallest: Asia, Africa, North America, South America, Antarctica, Europe, and Australia.

1492: An Ongoing Voyage What Came To Be Called “America”

By 1492 people had lived in the Western Hemisphere for tens of thousands of years. For much of this time it is believed that they experienced virtually no recorded, sustained contact with other parts of the world&mdashEurope, Africa, or Asia.

Millions of people lived in an area some five times the size of Europe. In strikingly diverse habitats and climates they developed possibly the most varied and productive agriculture in the world. Their lifestyles and belief systems differed widely and they spoke hundreds of distinct languages.

Throughout the hemisphere, states and centers of high civilization had risen and fallen. The dynamic Mexica (Aztec) and Inca empires were still expanding at this time and internal migration and warfare were common. The peoples did not see themselves as part of an entity. Only later would this area be given a unifying name&mdashAmerica&mdashand the people labeled &ldquoIndians&rdquo by Europe.

We have focused on five geographical areas of the region to represent the variety and complexity of peoples and cultures before 1492: the Caribbean, Middle America, the Andean region, the South Atlantic, and North America. In order to understand what came to be called America we are often dependent on European observations.

The Caribbean&mdashIsland Society

The largest group of people living in the islands of the Caribbean were the Taínos. Their villages were governed by chieftains, or caciques, who enjoyed some distinctions of rank but received tribute in times of crisis only. Related families lived together in large houses built of poles, mats, and thatch.

The Taínos were known for their fine wood carving and hammocks woven from cotton. Not a particularly warlike people, they played ceremonial ball games, possibly as a substitute for warfare and as an outlet for competition between villages and chiefdoms.

The other major group living in the Caribbean were the more mobile and aggressive Caribs, who took to the sea in huge dugout canoes. By the late 15th century, the Caribs had expanded into the smaller islands of the eastern Caribbean from the mainland, displacing or intermingling with the Taínos.

Oviedo came to America in 1514, where for over thirty years he compiled detailed ethnographic descriptions of the goods, products, peoples and customs of the Caribbean and Central America. He introduced Europe to a wide variety of previously unheard of New World &ldquoexotica&rdquo such as the pineapple, the canoe, the smoking of tobacco, and the hammock.

The hammock was perfected in the Caribbean and Brazil and was first introduced to Europeans during Columbus' first voyage of 1492.

Hammock in Fernández de Oviedo y Valdés, La Historia general y natural de las Indias. (Seville, 1535). Rare Book and Special Collections Division, Library of Congress

Middle Atlantic Cultures

Before 1492, modern-day Mexico, most of Central America, and the southwestern United States comprised an area now known as Meso or Middle America. Meso American peoples shared many elements of culture: pictographic and hieroglyphic forms of writing monumental architecture a diet primarily of corn, beans, squash and chiles the weaving of cotton cloth and extensive trade networks. While most people lived by working the land, many societies also included nobles and priests, warriors, craftsmen, and merchants.

The Mexica (Aztec) had formed a powerful state in the central valley of Mexico and conquered many neighboring states by the late 15th century. The bustling island capital, Tenochtitlan, with a population of perhaps 200,000, was located in the middle of Lake Texcoco. Groups like the Tarascans in the west and Zapotecs to the south, however, remained relatively independent. Even states that had been absorbed by the Mexica retained their rulers as well as their religion, language, and lands.

This highly accurate calendar was developed by the people of Mexico prior to 1492. The tonalpohualli, or sacred calendar, ruled the life of each Mexica and was consulted on all important occasions. It was made up of 260 days, or 20 months of 13 days.

Mexican Calendar in Mariano Fernández de Echeverria y Veytia, Historia del orígen de las gentes que poblaron la America septentrional [early 19th century manuscript facsimile] as Calendar wheel no. 7. Peter Force Collection, Manuscript Division, Library of Congress

The Tarascans inhabited Michoacán, an area west of Tenochtitlán (present-day Mexico City) and south of Guadalajara. This illustration depicts schematically various occupational groups existing before the coming of the Spanish. Groups of figures sit, each with an object or symbol such as a net, a loom, a bow and arrow, a writing instrument, feathers, etc., that identifies the occupation of a specific group. A couple of figures in the upper part of the illustration sit alone and are identified as being the Cazonci and su gobernador (their governor).

This well-illustrated manuscript from Mexico chronicles the history and customs of the Tarascan people before as well as during the Conquest in the area of Michoacán. Although written by a Franciscan friar, it is largely based on the accounts of informants among the Tarascan nobility and priests, thus essentially expressing an indigenous point of view. The text and numerous illustrations describe the government, customs, and elaborate society of the Tarascan people.

Professions of the Tarascan People, Mexico. Occupational Groups. Ink and wash drawing. In Relacíon de las ceremonias y ritos y población y gobierno de los indios de la provincia de Mechoacán compiled by Fray Jeronimo de Alcala (?). [19th century manuscript facsimile of the ca. 1540 original]. Peter Force Collection, Manuscript Division, Library of Congress

The Oztoticpac (Mexico) Lands Map is a central Mexican pictorial document with Spanish and Nahuatl writing showing litigation surrounding the Oztoticpac estate within the city of Texcoco, ca. 1540. Its glyph, a symbolic figure, corresponds to the name &ldquoabove the caves&rdquo (oztotl,cave icpac, above), a hill stylized in the shape of a woman. The document on pre-European amatl paper involves the land and property ownership of the ruler of Texcoco who was executed during the early days of the Spanish Conquest in the Central Valley of Mexico. The execution left in its wake litigation involving ownership of properties claimed by various sons of Nezahualpilli, the lords of Texcoco.

Most of the drawings on the map are plans of fields with indigenous measurements and place glyphs. Near the upper left is the plan of several houses within a precinct. On the upper right is a map showing about seventy-five plots of land. Additional fields are drawn at the lower right. Nahuatl and Spanish descriptions as well as three long Nahuatl texts include mention of Tollancingo, Oztoticpac, Tezcuco, Don Carlos, and Don Hernando.

In the lower left of the map are depictions of tree grafts showing European fruit tree branches grafted to indigenous tree trunks, uniquely displayed among all known Mexican Indian pictorial documents. Twenty trees, identified as pomegranates, quinces, apples, pears, etc., are shown. Also, as far as it is known, this is the earliest recorded lawsuit or conflict in horticultural literature anywhere in the world.

Oztoticpac, Mexico, ca. 1540, in The Oztoticpac Lands Map. [Mexico, ] ca. 1540. Manuscript on amatl paper. Geography and Map Division, Library of Congress

The Andes&mdashLife in the Highlands

Organized states and advanced cultures had long flourished in the Andean mountain region. The semi-arid highlands were the center of the far-flung Inca empire, Tahuantinsuyu, that extended from today's Chile to Colombia. Cuzco, the capital, was located at 10,000 feet above sea level.

Impressive adaptations to this unique environment allowed civilizations to thrive at higher altitudes than anywhere else in the world. The Andean peoples had learned to freeze-dry foods by taking advantage of the daily extremes of temperature at high altitudes. They kept herds of llamas and alpacas in the altiplano, weaving textiles from the wool. Using irrigation and terracing, they developed varieties of potatoes at high altitudes grew corn and coca at lower levels and raised cotton in the lowlands. They were knowledgeable miners, fine metalworkers, and great builders.

A rotating system of labor for public works that was traditional among Andean peoples was used to construct thousands of miles of roads. These roads greatly facilitated the movement of troops, peoples, and goods.

The huge fortifications surrounding the Incan capital of Cuzco, built to protect and to solidify Incan control, are outstanding examples of the advanced engineering techniques of Andean peoples. Stones of several tons in weight were precisely cut and placed in jigsaw-like fashion, without the aid of mortar, to form massive walls. These stone structures have withstood numerous earthquakes during the intervening centuries.

Sacsahuaman, Peru. Photoreproduction from original photograph. Prints and Photographs Division, Library of Congress

This magnificent center of Incan culture, high in the Andes, is testimony to the extraordinary construction capability of Andean peoples (i.e., intricate stone construction without the aid of mortar) before the arrival of the Spanish in the early 16th century.

Ruins at Machu Picchu, Peru. Photoreproduction from original photograph. Prints and Photographs Division , Library of Congress

South Atlantic Peoples

The coastal areas of eastern South America and the interior of the Amazon basin were home to several million people at the end of the 15th century. This enormous area, bordering the Andes mountains on the west and the Atlantic Ocean on the east, extends from present-day Argentina to the Guianas.

Socio-political structures were usually not highly developed in this area. The Tupí-speaking groups lived in villages in which related families resided together in large houses. They practiced slash-and-burn agriculture, and hunted and fished using blow guns and poison-tipped arrows. Manioc, a tuber, was their staple crop. They engaged in warfare and some groups practiced ritual cannibalism. Tupí groups eventually overcame the Tapuyas, mobile hunters and gatherers.

North America&mdashDiverse Societies

In the 16th century, North America&mdashoccupied today by Canada and most of the United States&mdashwas home to hundreds of groups speaking a striking variety of languages and dialects. They lived in diverse settings, from the Algonquian of the eastern woodlands, to the Caddo and Wichita of the grassy Midwestern plains, and the Taos of the arid southwest.

Some North American tribes, like the Iroquois, were organized into large political confederations. Extensive trade networks - sometimes operating over long distances - allowed for the exchange of products such as animal skins, copper, shells, pigments, pottery, and foodstuffs. Housing styles varied from covered wood to multilevel dwellings constructed of stone and mud, and transportable shelters made of poles and animal hides. Many tribes played games such as lacrosse and stickball. Religion was an integral part of daily life, tying them to the land, to other living things, and to the spirits that animated their world and provided order to social relations.

The people of Secotan lived in permanent villages near today's North Carolina Outer Banks. Like the northern Algonquians, they farmed collectively in the growing season and dispersed into family units to hunt during the colder months.

The engraving, based on a drawing made by John White in the 1580s, shows careful management and use of the land. Crops include tobacco and pumpkins, corn in three stages of growth, and sunflowers, while domesticated deer graze in the adjoining woods. The buildings include family units and storehouses for the surplus corn.

The Secotan traded with other groups like the powerful Mandoag of the Piedmont area of North Carolina, who acted as middlemen in the copper trade.

Secotan Village Showing Space Utilization in Theodor de Bry, Americae pars decima, Openheim, 1619, as Indian village of Secotan. Rare Book and Special Collections Division, Library of Congress

Where did the first Americans come from? New clues from new studies.

A pair of studies seek to answer questions about the first inhabitants of the Americas: Where did they come from, and how did they get here?

Who were the first Americans? Two research papers this week have arrived at contrasting interpretations.

One study, published Tuesday in the journal Science, proposes that the earliest Americans had singularly Siberian origins, crossing into the continent via the Bering land bridge in a single wave. Another, published Tuesday in Nature, suggests that some early Native Americans may have had genetic roots in Australia and its neighboring islands, a region known collectively as Australasia.

The peopling of the Americas is a matter of great anthropological and archaeological interest. We see evidence of unique culture on the continent over 10,000 years ago, but exactly how these populations arrived on the continent, and from where, has been debated for decades. Scientists generally agree that the first Americans crossed over from Asia via the Bering land bridge, which connected the two continents.

This exodus most likely began between 20,000 and 40,000 years ago. But some researchers have argued that Alaskan glaciers would have blocked entry into North America. The Beringia standstill hypothesis suggests that human populations would have remained stranded on this land bridge for some 15,000 years before ice melt finally allowed clear passage into the continent. From there, this main emigrant population would have split and diversified into many different first cultures.

Experts have noted that some early American skeletons, most older than 8,000 years, were found with physical features that seemed to contrast with those of historic and modern Native Americans. Some younger samples from South America also had these distinguishing traits.

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“They have suggested that this morphology matches more closely with Australasian populations,” says Pontus Skoglund, who co-authored the Nature study. “But there has always been this question of how statistically informative this morphology is, and to what extent this actually reflects population relationships.”

Using genomic data from Native American populations in South America and Central America, Skoglund and his colleagues found a surprising pattern. In some of these populations, they found a small degree of Australasian genetic ancestry.

“We found the peak of that signal in Brazil, which is also where people have suggested that the last populations with this morphology existed,” Skoglund says. “We don’t think that it’s likely that there was a population much more closely related to Australasians than to the Native Americans of today. But perhaps this is one step toward an explanation.”

A genetic link between Amazonian Native Americans and Australasians, Skoglund says, was previously unknown, and could have serious implications.

“I think almost no geneticists would have expected this,” Skoglund says. “What it tells us in terms of history, which is more important, is that there was a greater diversity of Native American ancestral populations than people previously thought.”

Skoglund and colleagues propose that, just before heading for the Americas, ancient Siberian populations could have mixed with an Australasian "Population Y." But the "how" and "when" are confined to mystery. The genetic data, Skoglund says, simply doesn’t tell us about that.

“My speculation is that there was a population quite closely related to Australasians in Northeast Asia around the time of the peopling of the Americas,” Skoglund says. “This population could have mixed with other populations to form the ancestral population of Native Americans. But there were perhaps multiple pulses of people into the Americas, and they had slightly different proportions of this ancestry. But which of the pulses came first and which different routes they took, we just don’t know.”

“The genetics have so far suggest that, in terms of ancient migrations, there was only a single one,” Skoglund adds. “There were a few additional migrations in the northern parts of the Americas, but those were more recent events.”

Similar genomic testing conducted by UC Berkeley geneticist Rasmus Nielsen supports the notion of a single migration. But it also challenges the Beringian standstill hypothesis in the process.

“We wanted to test it by dating the divergence time – that is, the split time between populations that now live in Siberia and East Asia, and the Native Americans,” Nielsen says. “How long since they had a common population that lived in Siberia or somewhere in Asia? Using a number of new techniques and data, we could date that relatively precisely to be about 23,000 years ago.”

Given this approximation, a Beringian standstill would have been impossible.

“The first people appear in the Americas 14,000 or 15,000 years ago,” Nielsen says. “That doesn’t leave time for a Beringian standstill. They had to split off about 23,000 years ago, move all the way through Asia, and cross the land bridge into the Americas in 7,000 to 8,000 years. So clearly there was no 15,000-year Beringian standstill. There could have been a little bit of a standstill, but nothing like 15,000 years.”

Nielsen’s research offers a broader view of settlement. Migration would have occurred in a single wave, Nielsen says, before splitting into two main populations.

“We see that mostly all Native Americans are descendants from a migration wave into the Americas, maybe 20,000 years ago,” Nielsen says. “You see the first unique American culture about 13,500 years ago, which spreads through much of the Americas. Right around this time, we see that the Native American population first began splitting up. We find two major groups – what we call the southern group and the northern group.”

Nielsen says his colleagues found just two exceptions to their findings. The study doesn’t account for Inuit populations in the north because they arrived later, bringing a distinctive culture with them.

“The other little exception, which was very interesting, was that we found signs of some genetic affinity between Brazilian Native Americans and Melanesians,” Nielsen says. “They were just slightly more related than they really should have been, given previous data.”

Like Skoglund and colleagues, Nielsen’s team found Australasian ancestry in modern Native American people. This led them to investigate another hypothesis for the peopling of America – one Paleoamerican hypothesis, which suggests that the first people to come to the Americas were not from Siberia, but rather Australians and Melanesians who traveled by boat.

“We find a hint of evidence for this hypothesis in some South American populations,” Nielsen says. “We managed to extract some DNA from ancient samples of supposed Paleoamericans, who display more Australian and Melanesian-looking traits. But do these individuals actually have any genetic affinity with Australians and Melanesians? When we tested that, we found that the answer was no. They are clearly related only to modern Native Americans. We think this is evidence of a later migration, perhaps one that happened on a coastal route along the western coast about 8,000 years ago.”

According to Nielsen and Skoglund, both studies rely on the same genetic signals. But different interpretations of those signals resulted in a few contrasting conclusions.

“They saw the exact same signal, and they have even stronger evidence for that signal,” Nielsen says. “They feel, as was our first hunch too, that this may be support for a Paleoamerican hypothesis. But if so, we should be able to see evidence of it in the ancient DNA, and we don’t.”

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But interpretations aside, both studies share a common goal – to answer the basic questions about how the Americas were populated.

“This has been a really old, very controversial question with lots of different theories,” Nielsen says. “What we have shown is that, with the caveat of this little signal in the South Americas, we’re back at the most boring, most vanilla theory – one big migration that happened around 20,000 years ago. We have no support for all of these more fanciful theories.”

New Evidence Suggests Humans Arrived In The Americas Far Earlier Than Thought

(Left) A close-up view of a spirally fractured mastodon femur. (Right) A boulder discovered at the Cerutti Mastodon site in San Diego County thought to have been used by early humans as a hammerstone. Tom Démeré/San Diego Natural History Museum hide caption

(Left) A close-up view of a spirally fractured mastodon femur. (Right) A boulder discovered at the Cerutti Mastodon site in San Diego County thought to have been used by early humans as a hammerstone.

Tom Démeré/San Diego Natural History Museum

Researchers in Southern California say they've uncovered evidence that humans lived there 130,000 years ago.

If it's true, it would be the oldest sign of humans in the Americas ever — predating the best evidence up to now by about 115,000 years. And the claim has scientists wondering whether to believe it.

In 1992, archaeologists working a highway construction site in San Diego County found the partial skeleton of a mastodon, an elephant-like animal now extinct. Mastodon skeletons aren't so unusual, but there was other strange stuff with it.

"The remains were in association with a number of sharply broken rocks and broken bones," says Tom Deméré, a paleontologist at the San Diego Natural History Museum. He says the rocks showed clear marks of having been used as hammers and an anvil. And some of the mastodon bones as well as a tooth showed fractures characteristic of being whacked, apparently with those stones.

It looked like the work of humans. Yet there were no cut marks on the bones showing that the animal was butchered for meat. Deméré thinks these people were after something else. "The suggestion is that this site is strictly for breaking bone," Deméré says, "to produce blank material, raw material to make bone tools or to extract marrow." Marrow is a rich source of fatty calories.

Don Swanson, a paleontologist with the San Diego Natural History Museum, points at a rock fragment near a large horizontal mastodon tusk fragment. San Diego Natural History Museum/Nature hide caption

Don Swanson, a paleontologist with the San Diego Natural History Museum, points at a rock fragment near a large horizontal mastodon tusk fragment.

San Diego Natural History Museum/Nature

The scientists knew they'd uncovered something rare. But they didn't realize just how rare for years, until they got a reliable date on how old the bones were by using a uranium-thorium dating technology that didn't exist in the 1990s.

The bones were 130,000 years old. That's a jaw-dropping date, as other evidence shows that the earliest humans got to the Americas about 15,000 to 20,000 years ago.

"That is an order of magnitude difference. Wow," says John Shea, an archaeologist at New York's Stony Brook University who specializes in studying ancient toolmaking. "If it's correct, then there's an extraordinarily ancient dispersal to the New World that has a very different archaeological signature from anything left behind by recent humans."

Shea says it's different because Stone Age toolmakers usually leave behind stone flakes — sharp pieces broken or "knapped" from certain kinds of rock that serve as cutting implements. There were none at the California site. Another odd thing: no signs that the mastodon was butchered for the meat.

"This is weird," Shea says. "It's an outlier in terms of what archaeological sites from that time range look like everywhere else on the planet." He suggests these bones might have been broken up by natural causes — by a mudflow, perhaps, or by the trampling of animals sometime after the mastodon died.

Another skeptic is John McNabb, an archaeologist at the University of Southampton in England. His question: How did those people get to California?

Twenty thousand years ago, archaeologists agree, people did cross over to Alaska from Siberia, perhaps more than once. Sea levels were lower then and there was a land bridge connecting the continents. In an interview with the journal Nature, which published the California research, McNabb says that land bridge wasn't there 130,000 years ago. "The sea lane in between the two continents [was] wider [then]," he says, "so that's one problem with this: How do we get humans across?"

McNabb says what's needed to really prove that this is truly an archaeological site are bones from the people who got there.

The California team counters that it has spent over 20 years examining the evidence. "I know people will be skeptical with this because it is so surprising," says team member and archaeologist Steve Holen, "and I was skeptical when I first looked at the material myself. But it's definitely an archaeological site."

Holen, with the Center for American Paleolithic Research, says these early people could have come across in boats. As for the broken bones, he says the type of fracture isn't accidental. And the way the hammerstones and bones were distributed in the ground doesn't look natural.

One question the team can't answer is who these people were. A genetic technique that uses mutations in a population's genome as a sort of "clock" says the first common ancestor of Native Americans lived about 20,000 years ago. So if there were indeed earlier settlers, it could be they made an arduous migration from Siberia, only to die out without leaving any descendants.

Bring it home for us, Craig, by telling us what you believe is ultimately the real story of the populating of North America, and what surprised you most during your travels?

What I took away was that people came from everywhere. We think of the arrival of the first people as one group braving their way across a land bridge, when in fact it was many groups, many different languages, and technologies arriving at different times from different directions. This makes sense because that’s how we do things as humans. It’s not just one group. It is this complex story of many people, with many different stories.

For me, it was an opportunity to explore landscapes I wouldn’t normally go to, like an island off the coast of Siberia or crossing an ice field in Alaska. The most fascinating place I saw was a back woods river south of Tallahassee, Florida, where human evidence from 14,500 years ago was found. Just being in these swamps with a boat, surrounded by alligators and poison snakes, gave me a sense of coming into a landscape I didn’t know and encountering animals I wasn’t familiar with. There were many moments like this, where I felt this must have been something like how it was to be first in a place to have to figure out which direction is which, what animals you have to avoid, what plants you can eat or can’t touch. For me, this was a new beginning, a way of coming into my own continent.