A new book on anthropological genetics shakes up what we thought we knew about the first Americans. Instead of crossing by foot over the Bering Land Bridge, (a theory known as the Clovis hypothesis), geneticist Jennifer Raff suggests that early settlers in to the Americas likely came via what is known as the Kelp Highway. This is also called the coastal route theory.
Kelp Highway hypothesis: no Bering Land Bridge
Archaeologist Jon Erlandson first developed the Kelp Highway hypothesis. It evolved from a similar theory about the early human settlement of Australia, Melanesia and Japan, which eventually expanded into Russia and Alaska. Eventually, these longtime Beringians traveled along a Pacific coastal route to settle in the Americas.
Erlandson’s hypothesis suggests that these ancestral peoples found their way to Chile and California’s Channel Islands at least 14,500 and 13,000 years ago, respectively. This doesn’t necessarily mean that those locations were the initial entry points for inward migration into the Americas — just that human activity at those sites predates any known activity further inland.
Erlandson posits that settlers used dense seaweed forests to survive and navigate their surroundings. The kelp forests along the Pacific Rim once flourished far beyond today’s patches. Those vast swaths of kelp would have made for easier and safer travel, as the nutrient-dense sea vegetable not only fosters an abundance of edible sea life, it dampens waves in the same way that swimming pool lanes do — important for those primitive, vulnerable boats.
Overall, prehistoric coastlines were much more hospitable to survival than inland areas, which featured harsher weather, more challenging terrain, and less food than the always abundant ocean.
Migration patterns according to the Kelp Highway hypothesis. Image: National Geographic
Coastal Route theory and the Americas
In her book Origin: A Genetic History of the Americas, Raff combines data supporting the Kelp Highway hypothesis with information from archaeological digs, genetics, and linguistics. She argues that the Bering Strait was a homeland, not a passageway. People inhabited it for thousands of years, first brought by coastal walkers from western Melanesia and Japan.
“Beringia…was a place where people lived for many generations, sheltering from an inhospitable climate and slowly evolving the genetic variation unique to their Native American descendants.” she wrote.
Migration patterns according to Kelp Highway or Coastal Migration theory. Image: Science Mag
Two critical pieces of evidence “strongly suggest” that when various groups in Beringia began migrating, they did so along the coast rather than inland.
First, Raff points out, coastal America was open by 16,000 years ago, whereas the ice-free corridor between the two ice sheets wasn’t a viable route until about 12,500 years ago. Second, the populations split so swiftly — almost instantaneously, according to their genetics. This fits more closely with southward migration by boat rather than overland.
She admits, however, that we are still beginning our journey of understanding the multi-pronged outreach of humanity from our African beginnings.
