Exploring Coastal Migration: Evidence for Early Human Boat Voyages

By: Matt Kraemer

Homo sapiens have survived and traversed Earth for over 300,000 years (Callaway, 2017). Throughout that time, humans have proven themselves to be masters of innovation. When faced with formidable animals, they crafted weapons to level the playing field. In search of new resources, they relied on the stars to navigate vast, unfamiliar landscapes. And when confronted with impassable rivers, they built boats, allowing them to cross even the most treacherous waters.

This adaptability and ingenuity paved the way for new theories, including the possibility that humans migrated into the Americas by boat.

The Coastal Migration Theory

Credit: National Geographic Society

The peopling of the Americas has been a subject of significant debate for over half a century. Initially, scholars favored the Clovis First Hypothesis, which proposed that the first humans entered the Americas by traversing an Ice-Free Corridor (IFC) that opened between the Laurentide and Cordilleran Ice Sheets around 13,000 years ago. 

However, Tom Dillehay’s groundbreaking discovery of Monte Verde, Chile in the 1970s provided evidence of human occupation dating to at least 14,000 years ago—possibly even earlier—challenging this long-standing paradigm. Since then, researchers have explored alternative migration models.

One increasingly supported theory suggests that the first peoples to enter the Americas likely arrived by boat, traveling along Pacific Rim coastlines from Northeast Asia through Beringia and eventually into the Americas (Braje et al. 2017). Exposed continental shelves during this time may have provided migration pathways, with the Pacific Northwest serving as one of the earliest areas of settlement (Gustas and Supernant, 2017). 

This theory is further supported by the fact that the IFC was not a viable migration route until around 13,800 years ago. Therefore, any pre-Clovis migrations could not have occurred through this corridor, making the coastal route the most likely alternative (Clark et al., 2022).

Evidence of Sea-faring People

It should come as no surprise that the first people to migrate into the Americas likely traveled by boat, given the long-standing evidence of coastal and open-water navigation. 

The initial colonization of Australia, for example, required seafaring technology. Similarly, the settlement of the Kuril Islands 17,000 years ago demonstrated advanced maritime capabilities, with humans successfully crossing 66 km of open water (Balme, 2013; Royer and Finney, 2020).

Further evidence of early seafaring comes from Western Melanesia, where humans reached islands nearly 40,000 years ago. Around 35,000 years ago, Upper Paleolithic mariners successfully navigated to the Ryukyu Islands near Taiwan, while artifacts found on Kozushima confirm that humans traveled over 25 km from the mainland using boats (Erlandson and Braje, 2011). 

These examples demonstrate that early humans were not only capable of seafaring but also relied on it to explore and settle new regions.

Implications

While boats enabled humans to reach otherwise inaccessible regions, their reliance on coastal migration may have hindered the archaeological record.

During the Pleistocene epoch, especially before the Last Glacial Maximum (LGM), the world’s landscape was drastically different from today. Sea levels during the LGM were approximately 400 feet lower on average, exposing the Bering Land Bridge, Sundaland, and extending the coastlines of major continents (Smithsonian Institution, 2018.). Many potential archaeological sites along these ancient coastlines have likely been submerged by rising sea levels, erasing critical evidence of early migrations.

Additionally, organic materials such as wood and plant-based tools decompose over time, making it even more difficult to find direct evidence of seafaring technology. These factors highlight the challenges in reconstructing early human migration patterns and underscore the need for innovative research methods to uncover submerged sites (Smithsonian Institution, 2018).

Australasian Genetic Markers in South America

Credit: Ioannidis, A.G., Blanco-Portillo, J., Sandoval, K. et al. Native American gene flow into Polynesia predating Easter Island settlement. Nature 583, 572–577 (2020).

The advent and widespread circulation of DNA testing have been a major boon to anthropological thought. One of the most fascinating examples of this comes from a study analyzing the DNA of Indigenous groups from South America.

In 2015, researchers discovered that some Indigenous peoples in the Brazilian Amazon carried a genetic signal linked to Australasian ancestry, a finding that suggested distant connections to Native Australians and Melanesians. This signal, called the "Y signal" from the Tupi word ypikuéra (ancestor), has since been identified as more widespread across South America than initially thought. Recent studies reveal its presence not only among Indigenous Amazonian groups like the Karitiana and Suruí but also in populations like the Xavánte of Brazil’s central plateau and Peru's Chotuna people, descendants of the Mochica civilization. This genetic evidence suggests the Y signal may have been introduced by some of the earliest migrants to South America.

What makes this finding particularly compelling is the absence of Australasian DNA among Indigenous groups in North America. The genetic signal, known as Population Y, does not persist in modern Eurasian populations, nor does it appear in other Native American groups. This absence challenges conventional migration theories. If Aleutian Islanders or their ancestors had interacted with an Australasian-linked group in the north or traveled southward to the Amazon, genetic evidence should have been detected along their migration route (Smithsonian Magazine, 2015).

This gap implies multiple migrations into the Americas by distinct groups and raises fascinating questions about the route taken by these early travelers. How could a group have reached the Amazon from Beringia without leaving a genetic trace in North America? One possibility is that they traveled down the Pacific coast by boat before venturing inland, bypassing much of the continent. However, it is puzzling that such a group, after thousands of miles of migration along the coast, never ventured inland before settling in the Amazon.

“There is an entire Pacific Ocean between Australasia and the Americas, and we still don’t know how these ancestral genomic signals appeared in Central and South America without leaving traces in North America,” said Andre Luiz Campelo dos Santos, Ph.D., first author, archaeologist, and postdoctoral fellow in FAU’s Department of Electrical Engineering and Computer Science (Santos et al., 2022).

Perhaps climate change has erased evidence of a coastal migration, or researchers have yet to uncover the DNA in Indigenous North American populations. While some may find the idea outlandish, could these groups have bypassed North America entirely, island-hopping across the Pacific Ocean to South America?

Sweet Potatoes and Polynesian-South American Contact

While there is no hard direct evidence of advanced seafaring technology, early humans were clearly capable of navigating at least 66 km of open water (Balme 2013; Royer and Finney 2020). Though this distance is far shorter than a trans-Pacific journey, it demonstrates that early groups possessed both the ability and ingenuity to undertake substantial voyages. Humans reached the remote and enigmatic Easter Island by island-hopping from Polynesia—an island located approximately 3,686 km from modern-day Chile.

Another fascinating wrinkle in this compelling theory is the presence of the South American sweet potato on Easter Island and other Polynesian islands. It is possible that sweet potato seeds were transported naturally by birds, ocean currents, or wind. However, some researchers suggest that humans carried the crop with them as they traveled between the islands and the South American mainland.

If this theory is correct, it implies that Polynesians not only traversed the Pacific via island-hopping but also settled in South America while maintaining contact with their home islands. Alternatively, it could indicate that Native Americans were capable of navigating from South America to Polynesia, bringing the sweet potato with them. This hypothesis was famously tested during the Kon-Tiki expedition in 1947, when Thor Heyerdahl and five companions successfully sailed from the western coast of South America to Tahiti on a balsa wood raft, using only traditional methods and without modern equipment (Rull, 2019).

Conclusion

The theory that early human migrations to the Americas relied on seafaring vessels has become more credible with the support of compelling evidence. As research continues, it will be fascinating to see how new discoveries help refine this theory further.

Future genetic studies, archaeological findings, and advancements in paleoenvironmental reconstructions could shed further light on how Australasian ancestry reached South America. Whether through coastal migration, island-hopping, or the traditional land migration model, the presence of the "Y signal" challenges conventional views of early human movement in the Americas.

The now widely accepted idea that humans traversed the world using boats opens the door to more nuanced migration theories. Navigating coasts, rivers, and perhaps even oceans allowed humans to reach areas they might not have otherwise accessed. While debates and new theories will continue to evolve, one thing remains certain: human migrations are far more complex than once believed.

A nuanced, open-minded, and thoughtful approach is essential to deepening our understanding of the past.

Sources:

Balme, J. 2013. "Of Boats and String: The Maritime Colonization of Australia." Quaternary International 285:68-75.

Braje, T., Dillehay, T., Erlandson, J., Klein, R., Rick, T. 2017. "Finding the First Americans." Science 358:592-594.

Clark, J., Carlson, A. E., Reyes, A. V., Rood, D., Froese, D., Young, J. M., Norris, S. L., Margold, M., and Dredge, L. 2022. "The Age of the Opening of the Ice-Free Corridor and Implications for the Peopling of the Americas." Proceedings of the National Academy of Sciences 119(14): e2118558119. https://doi.org/10.1073/pnas.2118558119.

Erlandson, J., Graham, M., Bourque, B., Corbett, D., Estes, J., Steneck, R. 2007. "The Kelp Highway Hypothesis: Marine Ecology, the Coastal Migration Theory, and the Peopling of the Americas." The Journal of Island and Coastal Archaeology 2:161-174.

Gustas, R., Supernant, K. 2017. "Least Cost Path Analysis of Early Maritime Movement on the Pacific Northwest Coast." Journal of Archaeological Science 78:40-56.

Royer, T., Finney, B. 2020. "An Oceanographic Perspective on Early Human Migrations to the Americas." Oceanography Society 33:32-41.

Santos, Andre Luiz Campelo dos, et al. 2022. "Ancient DNA Analysis Unravels the Early Peopling of South America." Florida Atlantic University News Desk, Nov. 2. https://www.fau.edu/newsdesk/articles/ancient-dna-south-america.

Smithsonian Institution. 2018. "Sea Level Rise." Smithsonian Ocean. Retrieved from https://ocean.si.edu/through-time/ancient-seas/sea-level-rise.

Smithsonian Magazine. 2015. "A DNA Search for the First Americans Links Amazon Groups to Indigenous Australians." Smithsonian Magazine, July 21. Retrieved from https://www.smithsonianmag.com/science-nature/dna-search-first-americans-links-amazon-indigenous-australians-180955976/.

Rull, V. 2019. "Human Discovery and Settlement of the Remote Easter Island (SE Pacific)." Quaternary 2(2): 15. https://doi.org/10.3390/quat2020015.

About the Author: 

Matt Kraemer earned a master's degree in anthropology and a certificate in archaeology from Monmouth University in 2023. Since then, he has worked as a professional archaeologist in the Pacific Northwest, Mid-Atlantic, and Northeast regions. His primary research interests focus on the evolving theories regarding the peopling of the Americas during the Pleistocene.

You can find Matt on LinkedIn here.