By reconstructing 20,000 years of coastal history, a new study led by Chilean researchers reveals how dense kelp forests of the South Pacific may have provided stable and predictable conditions for early human populations in a changing climate. By integrating ecological modeling with archaeological evidence, the study offers a novel perspective for South America, expanding the geographic scope of the so-called “Kelp Highway Hypothesis.”

Over the past four decades, the narrative of the peopling of the Americas has been anchored to the land: groups of megafauna hunters crossing frozen steppes in an epic journey through Beringia. More recently, archaeological sites such as Pilauco, Monte Verde, and Tagua Tagua (Chile), Pedra Furada (Brazil), and Piedra Museo (Argentina) have also contributed to the discussion of early settlement in South America, including via coastal routes—an idea that has gained traction in scientific debate in recent years.

Along these lines, the ocean has begun to reclaim its place in this story. One of the most influential ideas in this shift is the “Kelp Highway Hypothesis,” which proposes that early humans moved along the Pacific coast, taking advantage of rich and predictable marine ecosystems.

Until now, most of the evidence for this hypothesis has been concentrated in the Northern Hemisphere. However, a study recently published in Frontiers in Ecology and Evolution provides key new insights from the southern part of the continent, showing that the South American Pacific coast may have offered similar conditions for thousands of years.

Kelp forests, or macroalgal forests, are considered true “ecosystem engineers”: they not only support extraordinary biodiversity, but also create productive and relatively predictable environments over time. According to the study’s authors—from Universidad Adolfo Ibáñez (UAI), Universidad Austral, and the Millennium Institute in Coastal Socio-Ecology (SECOS)—this stability is precisely what may have facilitated the movement and settlement of human populations along the South Pacific.

Mapping a submerged world

To reconstruct this past, the team used species distribution models (SDMs) combined with paleoclimatic data, projecting the presence of macroalgal forests across three key periods: the Last Glacial Maximum, the Mid-Holocene, and the Medieval Warm Period.

They then cross-referenced these maps with evidence from 38 coastal archaeological sites between Peru and Patagonia. The result was consistent: a recurring overlap between areas with a high probability of kelp forest presence and zones of early human occupation.

“What archaeologists propose is that macroalgal forests form a continuous habitat; that is, you encounter them repeatedly along the coastline,” explains Bernardo Broitman, a SECOS researcher and academic at the Faculty of Liberal Arts at UAI. “They offer a set of resources that are, to some extent, predictable—you know where to find them. It is a habitat rich in resources year-round, which is vital for a mobile population.”

Rather than a single linear route, the findings suggest the existence of a mosaic of productive coastal habitats that together may have functioned as ecological corridors for early human populations.

The challenge of finding what time erases

Despite their importance, algae are difficult to trace in the archaeological record. Unlike shells or bones, their organic material degrades rapidly, limiting direct evidence of their use.

Carola Flores, an archaeologist and also a faculty member at UAI’s Faculty of Liberal Arts, emphasizes that the key lies in broadening the perspective. “The problem with studying algae in archaeological contexts is preservation. As organic materials, they degrade easily, and therefore direct evidence is scarce,” she explains.

However, she notes that there are multiple ways to infer their importance. “The relevance of these ecosystems can be observed through dried or charred remains, but also indirectly through fish, mollusks, and other species associated with these forests. Evidence shows multiple uses: as food, fuel, or raw material,” she adds.

Sites such as Monte Verde, in southern Chile, have provided some of the earliest evidence of algae use, showing that they were already part of the daily lives of human communities thousands of years ago.

A refuge at the end of the world

The study also reveals a key pattern. Over time, kelp forests have responded to climate changes by shifting toward the poles. After the last glaciation, their distribution expanded southward, following the availability of colder waters. Today, this same pattern is being observed again—but under the accelerated pressure of climate change.

“These poleward shifts have been documented in different parts of the world. It is a consistent response of these ecosystems to warming,” Broitman warns, adding that “in the case of Chile, the country’s latitudinal extent could offer refuges toward the far south, but that does not mean they are free from threat.”

Rising ocean temperatures, along with pressure from kelp harvesting, could fragment these ecosystems, affecting their persistence, particularly in northern Chile.

Kelp as a connector of history

Beyond reconstructing the past, the research proposes a new way of understanding the relationship between humans and coastal ecosystems. From the Atacama Desert—where macroalgae were used as fuel in contexts of scarce firewood—to the southern channels, these algae have been part of the ecological and cultural fabric of coastal societies.

By integrating ecological modeling with archaeological evidence, the study provides a novel perspective for South America, expanding the geographic scope of the “Kelp Highway Hypothesis.” “This approach allows us to connect the ecological past with human history. Modeling reconstructs where macroalgal forests may have existed, and archaeology shows that those same spaces were used by human communities, reinforcing their role as a resource base and a possible key in the formation of these coastal settlements,” explains Daniel González-Aragón, co-author of the study and researcher at the Universidad Católica de la Santísima Concepción.

Rather than confirming a single migration route, the findings reinforce the idea that marine ecosystems—and macroalgal forests in particular—may have played a key role as stable, productive, and connected environments, facilitating human occupation over time.

In that sense, protecting these ecosystems is not only an ecological task, but also a historical one. Because within their dense, lush waters lies not only biodiversity, but also part of the path our own species once followed.