When humans were walking around the west coast of current day Canada 13,000 years ago, they left behind footprints.
That's according to a new study published in the journal PLOS ONE that outlines the discovery of 29 human footprints found at the shoreline of Calvert Island in British Columbia.
According to an interview with the New York Times, anthropologist Duncan McLaren from the Hakai Institute and University of Victoria first found the footprints in 2014. During subsequent trips in 2015 and 2016, more emerged.
Based on each foot's outline, the study theorizes that they were left by two adults and a child. The footprints are embedded in clay soil. Layered with coarser sediment like sand and another layer of clay, the landscape's natural terrain may have helped preserve the ancient remnants. When radiocarbon dating was performed on samples, scientists determined they were made 13,000 years ago.
This would make them the earliest known footprints found in North America.
What Does It Mean?
"This finding provides evidence of the seafaring people who inhabited this area during the tail end of the last major Ice Age," McLaren said in a press release.
Previous studies support a theory that humans arrived in North America by migrating over an intact land bridge that connected Asia to Alaska. The theory suggests early Americans then migrated south along the west coast.
Looking for archaeological evidence of humans trekking south is difficult today. At the end of the last Ice Age, sea level in this region was six to ten feet lower, and today, dense forests blanket the coast. Much of the shore can only be reached by boat.
The study's authors say this rare find supports the idea that humans traveled south along a coastal route.
And Before That?
In 2007, DNA was extracted from a tooth found on Prince Wales Island in southern Alaska and revealed it to be 10,300 years old. Then, in 2008, a subsequent study analyzed modern and ancient genetic material and concluded humans arrived in the Americas no earlier than 15,000 years ago.
So where were we before that?
Human origins are thought to have originated in southeast Africa about 200,000 years ago, but a study published last year suggests evidence of early humans in Morocco about 300,000 years ago. From there, humans sailed east toward Australia or walked north into Europe and Asia, eventually reaching South America.
One study published in 2011 suggested that a warming period around 130,000 years ago may have given humans the opportunity to leave Africa. Increased rainfall would have created navigable rivers and more livable climates.
It's often estimated that humans did not leave Africa until about 60,000 years ago, but some evidence published earlier this year places humans in modern day Israel 120,000 years ago.
While finding the footprints in Canada are a clue to understanding human migration, the study authors emphasize it's just that—a clue.
More excavation and archaeological evidence will be needed to piece together the path humans first took into the Americas.