New Clues on Ancient Beringians
January 19, 2018
How and when did people first reach the Americas? It is generally agreed that humans arrived in the Western Hemisphere at least 15,000 years ago. They got there by crossing Beringia, a land bridge that once connected Asia and North America. (Beringia takes its name from the Bering Strait and Sea that now cover the former land bridge.) The details of this human movement have long been a mystery. Recently, however, ancient DNA found in Alaska has helped scientists learn about the timing and circumstances of the migration.
University of Alaska Fairbanks professors Ben Potter and Josh Reuther excavate the remains of two ancient infants along the Upward Sun River in Alaska. Credit: © Ben Potter, University of Alaska Fairbanks
In 2011, a team of archaeologists discovered the bones of two female infants along the Upward Sun River in Alaska. One was an infant who died a few months after birth. The other was a newborn or late-term fetus. The archaeologists determined that the infants died about 11,500 years ago. After the Upward Sun River infants died, their bodies were laid atop a bed of red ocher surrounded by antler points. Only small fragments of DNA from the younger infant were available to study. However, scientists were able to reconstruct the genome (the entire set of chemical instructions that control heredity in a human being) of the older infant.
This scientific illustration shows the ancient Upward Sun River camp in what is now interior Alaska. Credit: © Eric S. Carlson/Ben A. Potter/University of Alaska Fairbanks
Previous studies have shown that Native Americans are descended from one of two ancestral groups. The northern group produced most of the indigenous (native) people of Alaska and upper Canada. A southern group produced most of the indigenous people of the lower United States, Mexico, and Central and South America. The genome of the older infant revealed that she came from a very early group of Native Americans who were the ancestors of both the northern and southern indigenous groups. These original people are now known as the Ancient Beringians. The scientists’ work represents the first reconstruction of an Ancient Beringian genome. It provides key evidence to the theory that all living Native Americans are originally descended from the same group of people.
Despite the fact that the Upward Sun River infants shared a grave and seem to have been from the same community, their DNA shows a great deal of variation. This variation supports what is known as the Beringian Standstill hypothesis, which suggests that ancient Siberians entered Beringia and stayed there for thousands of years before they entered the Americas. This hypothesis proposes that ice age glaciers blocked their migration until about 15,000 years ago, when the glaciers began to melt and retreat. According to the Standstill hypothesis, much genetic mixing would have occurred in Beringia before movement into the Americas began. This helps explain why the two infants’ DNA shows such variation.
The remains of the Upward Sun River infants have shed much light on the migration of the Ancient Beringians. However, more ancient DNA must be gathered and studied before the Beringian Standstill hypothesis can be proven true. There are still many details about the populating of the Americas that remain a mystery.
