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Food, Health, and Eco-news
How Seaweed Made Our World
Following the “Kelp Highway” may be how humans spread across the globe. Why kelp? It’s where the food lives, and it’s food itself. 05/20/2021 by Temma Ehrenfeld

True miso soup doesn’t begin with miso, a fermented soybean paste, you may be surprised to learn. It begins with a broth called dashi, made by soaking dried kelp, called kombu, in cold water. You can add shavings of fermented skipjack tuna or bonito later. Dashi is at the heart of Japanese cuisine.

As it turns out, kelp may be at the heart of the story of humankind, of both our origins and our ancient migration out of Africa to the rest of the planet. In Slime: How Algae Created Us, Plague Us, and Just Might Save Us, journalist Ruth Kassinger gives us an excellent tour.

How seaweed made us smart

As Kassinger tells it, we can begin the story of humans and seaweed with our ancestors the Australopithecines. No more than five feet tall and covered in hair, they lived from roughly four to two million years ago. They had simian faces and long arms from tree-living but walked upright. The dense forests of their part of Africa were shrinking, creating a landscape of savanna, clumps of trees and lakes and marshes. These ancient hominins adapted by learning to walk and forage in marshes and along shorelines. To their original forest diet of leaves, fruits, nuts, and ants, they added the nutrient-rich eggs of shorebirds, freshwater clams and mussels, catfish, frogs and turtles—and marsh plants.

The extra protein was life-saving, as they didn’t have weapons to kill large animals. It was also a diet that gave pregnant females a little iodine, which helps build brain cells. Today, even mild shortages of iodine in the uterus can limit a baby’s intelligence (see “Iodine, Forgotten Nutrient From the Sea”).

Just as important, it also gave them omega-3 docosahexaenoic acid, or DHA, which triggers genes that help fetuses and babies build brains, and is also a major structural component of those brains. Baby fat is about three to four times richer in DHA per pound than adult fat, allowing for rapid brain development.

evolution of human skull
Australopithecus got a brain-boost to become Homo erectus through DHA-rich foods. Rediscovering seaside versions of those foods a million years later led to another brain-growth spurt for our immediate ancestor, Homo sapiens.

According to Stephen Cunnane, a metabolic physiologist at the University of Sherbrooke in Quebec, and Michael Crawford, director of the Institute for Brain Chemistry and Human Nutrition at Imperial College London, these nutrients in freshwater shoreline foods set humanity on its path towards larger, fatter, more resilient babies with bigger brains (Science Daily, 2006).

Homo sapiens evolved more than a million years later, in rainforest. Then a glacial age arrived, turning the land into a desert, nearly driving our species to extinction.

And then, food from the water may once again have changed human history. Around 165,000 years ago, a surviving remnant of Homo sapiens – perhaps with only a few hundred women of child-bearing age - may have taken refuge near Cape Agulhas on the southern tip of South Africa, settling in the Pinnacle Point caves.

There they could feast on mollusks and edible seaweeds growing on rocks, fed by the nutrient-rich Atlantic, observes Arizona State University’s paleoanthropologist Curtis Marean. Marine seaweed, especially kelp, and abundant shellfish that rock-wielding humans could easily open, offered much more iodine and DHA than humans had had before from freshwater plants and animals (Marean, 2012).

They thrived and multiplied on this rich ocean-based diet. The few people in small band, this theory holds, are ancestors to us all.

How kelp brought people to a new land

Kelp grows only in saltwater, most often along rocky coastlines, but below the water even at low tide. Kelp forests grow several meters tall.

Along the Pacific Rim coastline, kelp supports a huge ecosystem of shellfish, sea otters, and fish. Those forests might have been bigger and even more abundant in ancient times, anthropologists say.

According to Jon Erlandson, and his colleagues at the University of Oregon, when early humans fished among these sea forests, which broke the waves and kept them safe, they followed the kelp like a highway to the Americas. That Ice Age coastline was more complex than today’s, marked by inlets and bays—all rich in food (Braje et al, 2017; Erlandson et al., 2015, Erlandson et al., 2011).

Previously, scientists thought the first arrivals in the Americas were a people called the Clovis, named after the town in New Mexico where their distinctive tools were first identified. The Clovis were thought to have migrated on foot from Siberia across an Ice Age land bridge, Beringia, which brought them to Alaska about 13,000 years ago.

split screen with underwater kelp and above water rocky terraine
Underwater kelp forests, teeming with fish and edible themselves, sustained our earliest ancestors as they spread over the globe, according the “Kelp Highway” theory.

The “Kelp Highway” hypothesis points to evidence that people came to the Americas earlier, perhaps as early as 16,000 years ago. Imagine boats from the Kuril Islands (connecting present-day Japan and Russia) traveling along the coastline of Beringia or the shoreline of the Aleutians. They might then have paddled south along the Pacific coastline, eventually reaching Chile.

One site discovered by diving archaeologists off the coast of Chile dates back nearly 15,000 years, when any inland route would have been locked up in ice. An archaeological dig at California’s Channel Islands suggests a settlement from at least 13,000 years ago, probably too soon for the Clovis to have arrived from up north. The people there might have lived on black abalone, sea urchin, seals and other animals in the kelp forest – and consumed the kelp itself. Inland, the climate would have been harsher and food harder to catch.

The Ice Age coastline was lower than it is today. Rising ocean has made it harder to prove the “Kelp Highway” hypothesis. The most potentially revealing sites may be underwater and under meters of seafloor silt. The theory, though compelling, may never be entirely proved.

Will we be eating more seaweed?

Asians have loved seaweed throughout their history, but for other people – though it may be part of our shared, ancient history - it is culturally new.

Expect to see more seaweed on menus as we shift to a climate-smart food system. Marine algae grow quickly, need no chemical fertilizer or pesticides, and do not require freshwater or arable land (resources under great pressure) (Bleakley et al., 2017).

In the United States, we’re already eating nori – dried sheets of red algae - wrapped around our sushi, spirulina in smoothies, and kelp in miso soup and pickled in wakame salad.

Human beings came close to extinction in an Ice Age, and the sea fed us then, and in a real sense made us human. Will its abundant life – including its animals and plants - now become our primary food source again as we face a growing population on a stressed planet?




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