“As this island would only have been accessible by watercraft 13,000 years ago,” Dr. McLaren said, “it implies that the people who left the footprints were seafarers who used boats to get around, gather and hunt for food and live and explore the islands.”
They found their first footprint in 2014. While digging about two feet beneath the surface in a 20-square-inch hole, they saw an impression of something foot-shaped in the light brown clay.
In 2015 and 2016, they returned and expanded the muddy pit. They discovered several more steps preserved in the sediment. The prints were of different sizes and pointed in different directions. Most were right feet. When the team was finished they had counted 29 in total, possibly belonging to two adults and a child. Each was barefoot.
The researchers think that after the people left their footprints on the clay, their impressions were filled in by sand, thick gravel and then another layer of clay, which may have preserved them.
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Using radiocarbon dating on sediment from the base of some footprint impressions, as well as two pieces of preserved wood found in the first footprint, Dr. McLaren and his team found them to be 13,000 years old.
That would make them the oldest preserved human footprints in North America.
“It’s not only the footprints themselves that are spectacular and so rare in archaeological context, but also the age of the site,” said Michael Petraglia, an archaeologist from the Max Planck Institute for the Science of Human History in Germany who edited the paper for PLOS One but was not involved in the work. “It suggests an early entrance into the Americas.”
Dr. Petraglia said the footprints also provided strong evidence for the coastal movement hypothesis and he added that they may have traveled the so-called “Kelp Highway,” a hypothesis that underwater kelp forests supported ecosystems down the North Pacific coast that helped ancient seafaring people hunt, develop and migrate.
“The work is important because it shows the ‘real’ people, not just artifacts or skeletal remains,” said Steve Webb, a biological archaeologist at Bond University in Australia. “However, the footprints are limited in number and don’t shed light on activities or movement that tell us very much.”
He added that future hunts for footprints should keep in mind that not everyone from this time period walked around barefoot. If anthropologists are too busy searching for soles, toes and arches, they might miss clues from those who wore animal skin shoes.