Many years ago, large glaciers locked up much of the seawater, which exposed big stretches of land. In this lesson, you'll learn about the land bridge theory, which may explain how the first people made their way to North America.
What Is a Land Bridge?
Did past civilizations walk on water? Scientists think people used to walk from Siberia to Alaska, but there's one problem. These two lands are separated by a stretch of water called the Bering Strait. Those early humans didn't have any special skills that allowed them to walk on water, but they did have some help from the environment.
About 10,000 to 25,000 years ago, much of the land that makes up the continents of Asia and North America was covered with ice. This ice sucked a lot of the seawater into huge glaciers, which caused the sea level to drop so low that it exposed the land under the water.
Imagine standing on an island beach and suddenly the water turns into a giant ice cube. The water moves into the ice cube, leaving a strip of land that you can walk on to a nearby island. That land is called a land bridge, because it's a piece of land that connects two separate areas.
The Land Bridge Theory
Because of the exposed land between Siberia and Alaska, scientists developed a theory called the land bridge theory, which states that early animals and people traveled from Siberia to Alaska across a land bridge. Siberia is in Russia, and Alaska is part of North America, so this theory describes a possible way that the first people made their way to North America.
Why Did People Cross?
People who crossed the land bridge weren't looking for a new home - they were trying to survive by following their food supply.
When the land bridge was exposed, plants started to grow on it. The plants attracted all types of animals, including woolly mammoths, big wild cats, Arctic camels, bears, moose, and horses. People who lived during this time couldn't run to the grocery store for food. Instead, they had to follow herds of animals and hunt for their food, so as the animals moved across the land bridge, people followed.
How We Know About the Land Bridge
When the earth warmed after the Ice Age, the glaciers melted and covered the land bridge with water. With the land bridge gone, people could not go back to Russia, so they stayed in the new land and traveled across what is now the United States. We know these early people lived in the U.S. because they left us clues.
In the early 1900s, archaeologists discovered spearheads near a town in New Mexico, which is a southwestern state. An archaeologist is a scientist who studies past human life by digging up remains and artifacts.
When the scientists took the spearheads back to their labs, they compared them to spear points found at the land bridge and discovered that they were a match. These matching artifacts showed that the same people who once lived near the land bridge also lived in the southwestern United States.
The land bridge theory states that early animals and people traveled from Siberia to Alaska across a land bridge that was exposed during the Ice Age. Today, these two lands are separated by a stretch of water called the Bering Strait. Archaeologist provided evidence that this theory might be true when they found spearheads in New Mexico that match spearheads found near the land bridge.