No one knows exactly how people first came to the Americas, but the archaeologist Jon Erlandson thinks that kelp helped them do it.

Kelp covers much of the Pacific Rim coastline, supporting a vast ecosystem of shellfish, otters, and fish. Jon Erlandson, and his colleagues at the University of Oregon’s Department of Anthropology, suspect that kelp sustained the first American people after they arrived on a long ocean journey from Asia — a theory known as the “Kelp Highway Hypothesis.” These early humans may have fished among the sea forests, relying on giant algae to break waves and keep them safe, while following the seaweed like a road map to the New World.

Ancient settlers might have used “kelp highways” to survive and navigate their new surroundings.

For much of the last century, the most popular theory for how humans arrived in the Americas focused on a land migration from Asia. This theory proposed a journey across the ancient land bridge of Beringia from Siberia and into Alaska. From there, these Upper Paleolithic hunters moved into the interior following an ice-free corridor, created by retreating ice sheets that temporarily opened around 13,000 years ago. According to this version of events, the hunters reached the coastline later, when big-game prey, like mammoths and mastodons, dwindled in the interior.

But what if these ancient Americans arrived far earlier, by sea, and kelp paved the way for their survival? As long as 50,000 years ago, seafaring people from the western Pacific Islands colonized Australia. Between 40,000 and 30,000 years ago, they arrived in the islands of western Melanesia and Japan— setting them up for a leap across the Pacific pond via the Beringia coast that once linked Russia and Alaska. Another site discovered by diving archaeologists off the coast of Chile dates back 14,500 years, when the inland route to America was still locked up in ice sheets. As archaeologists turned up more and more evidence of ancient seafaring and fishing culture, the Coastal Migration Theory has gone from marginal to mainstream.

The Kelp Highway Hypothesis builds on this, exploring how seafaring settlers might have used kelp to survive and navigate their new surroundings. Experts believe that ancient kelp forests along the Pacific Rim were more productive and widespread than they are today. It would have been easier and safer for ancient people to travel at sea level, feasting on the creatures found in kelp forests and riding along kelp-calmed waters. Inland, they would have faced a harsher climate, more geographical obstacles and less abundant food. An archaeological dig at California’s Channel Islands shows that people settled at least 13,000 years ago, feasting on black abalone, sea urchin, seals and other animals commonly found in a nearby kelp forest.

Ocean Wise sustainable seaweed

Today, humans continue to rely on kelp, harvesting it for use in toothpaste, beer and ice cream.

Thousands of years later, humans are still relying on kelp. Kelp ash is used to produce soap and glass. Alginate, a carbohydrate found in kelp, helps thicken products such as jelly, toothpaste and even ice cream. Kelp is especially popular in Asian cuisine, as an ingredient in familiar dishes like miso soup. It also plays an out-sized role in removing carbon dioxide from the Earth’s atmosphere and slowing climate change. And kelp is absolutely essential to the creatures that make their homes in its forest, such as the adorable sea otters that live among the kelp beds and wrap themselves in its fronds while they rest.

Protecting kelp forests means that humans and animals can continue to benefit from kelp — just like this giant algae might have guided humans into the New World thousands of years ago.

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