New and fascinating discoveries provide hard evidence for the Aquatic Ape theory, evidence that was not known when Alister Hardy and Elaine Morgan first advocated for this idea. There is now substantial data proving that early humans undertook long maritime journeys, developed unique physiological adaptations, and lived lives closely tied to water. In this blog post, I will examine some of the compelling evidence that supports a semi-aquatic past for humans. These pieces of evidence meet the stringent criteria set by the anthropological community, which demands archaeological proofs for our evolutionary history, rather than merely examining our own bodily adaptations.
Long Early Maritime Journeys
Early human species undertook impressive sea voyages, as evidenced by discoveries of human fossils and stone tools on distant islands that have been separated from the mainland for millions of years. For instance, Homo sapiens reached Australia about 65,000 years ago, a journey that required crossing at least 70-100 km of open sea from Indonesia, traversing the significant biogeographical barrier known as Wallace Line (O'Connell, Allen, & Hawkes, 2010). Similarly, Homo heidelbergensis or Neanderthals reached Crete around 130,000 years ago, leaving hand axes behind and crossing water distances of approximately 40 km (Strasser et al., 2010).
Even more spectacular are the colonization events of Luzon in the Philippines, Socotra in the Indian Ocean, and Flores in Indonesia. The colonization of Luzon, evident from the discovery of Homo luzonensis dating back 67,000 years, required crossing the Huxley Line, another notable biogeographical barrier, involving a journey of at least 250 km from the nearest landmasses (Detroit et al., 2019). Evidence also suggests that Oldowan toolmakers reached Socotra several hundred thousand years ago, which would have required a sea journey of approximately 80 km from the African coast (Amirkhanov et al., 2009). Additionally, the colonization of Flores, marked by the discovery of Homo floresiensis, also known as the Hobbit, required a journey of around 30-40 km of open sea (Morwood, Oosterzee, & Sutikna, 2007).
It is likely that Socotra, Flores, and Luzon were places where more archaic human species could live relatively undisturbed for long periods. For instance, the discovery of Oldowan tools on Socotra, which first appeared around 2.6 million years ago and were made by the ancestors of Homo erectus, suggests a very ancient colonization of the island (Semaw, 2000; Amirkhanov et al., 2009). The first settlers on Flores and Luzon were also likely from species predating Homo erectus, based on analyses of the fossils of Homo floresiensis and Homo luzonensis, which exhibit some archaic features (Morwood, Oosterzee, & Sutikna, 2007; Detroit et al., 2019). Given that these are all very isolated islands, it is entirely possible that early hominids lived throughout much of Southeast Asia for extended periods but were eventually pushed out when Homo erectus settled in the region, surviving late only on islands far out at sea.
All this evidence indicates that humans have been well-acquainted with aquatic environments for a couple of million years and suggests that humans probably lived scattered throughout the maritime world of the Eurasian coastline. This is also a clear sign that they could build floating structures or boats to undertake these maritime journeys.
Clues from Kalambo Falls
One clue to how these early floating structures might have been constructed can be found at Kalambo Falls in Zambia. Archaeologists have discovered the oldest known wooden structures here, dated to around 476,000 years ago. These structures consist of two interlocking logs joined by an intentionally cut notch. The researchers behind this finding believe the structures were likely used as a stable platform in a wet environment, which may have included use as a raft or dock (Barham et al., 2023).
The preservation of these wooden structures was possible because they became waterlogged, meaning they were submerged in water and saturated, preventing decomposition by creating an anaerobic (oxygen-free) environment (Barham et al., 2023). This remarkable preservation provides further evidence of early humans' ability to use wood to create structures for aquatic activities.
Surfer's Ear: Evidence of Aquatic Adaptations in Early Humans
Surfer's ear, or exostosis, is a bony growth in the ear canal that develops from prolonged exposure to cold water. Research by Trinkaus, Samsel, and Villotte (2019) has shown that a significant percentage of both Neanderthal and early Homo sapiens fossils in Eurasia exhibit this condition. In a study examining 77 fossils with well-preserved ear canals, it was found that these early humans were frequently in cold water environments, likely for marine foraging activities (Trinkaus, Samsel, & Villotte, 2019).
In the study, 48% of the Neanderthal specimens investigated had Surfer's ear. While it was often difficult to determine their sex, among the identified Neanderthal women, three out of four had this condition (Trinkaus, Samsel, & Villotte, 2019). Similarly, Surfer's ear was prevalent in Homo sapiens fossils, with approximately 25% of Middle Paleolithic specimens (300,000 to 30,000 years ago) showing the condition. The prevalence was 20.8% during the Early/Mid Upper Paleolithic (50,000 to 30,000 years ago) and dropped to 9.5% in the Late Upper Paleolithic (30,000 to 10,000 years ago), indicating a change in lifestyle (Trinkaus, Samsel, & Villotte, 2019).
Interestingly, in the 19 sexable Early/Mid Upper Paleolithic Homo sapiens specimens, Surfer's ear was present in 16.7% of males and 28.6% of females. This suggests that more women than men exhibited this condition in early Homo sapiens (Trinkaus, Samsel, & Villotte, 2019). These findings support the hypothesis that women, due to their thicker layer of subcutaneous fat, were better suited to spending extended periods in water and were likely more involved in diving activities. This evidence highlights the significant role aquatic environments played in the lives of early humans.
Moreover, findings from Panama show that even people living in warm environments can develop Surfer's ear when they engage in deep diving where the water is colder. This observation is supported by the analysis of fossils dating back thousands of years (Arias-Martínez et al., 2019), further emphasizing the connection between human activity and aquatic environments across different climates and time periods.
Conclusion
These pieces of evidence collectively paint a compelling picture of how early humans thrived in and around water. From navigating long distances over open seas to developing physiological adaptations to cold water environments, much also indicates that women were perhaps more involved than men in diving activities during this time.
As we uncover more about our past, it becomes clear that our relationship with water has profoundly shaped our evolution. These findings not only challenge previous notions about early human behavior but also open new avenues for understanding the complexities of our development. The future of exploring our aquatic heritage lies in continued research and the growing field of underwater archaeology, promising even more fascinating discoveries.
Literature
Amirkhanov, K. A., Zhukov, V. A., Naumkin, V. V., & Sedov, A. V. (2009). Эпоха олдована открыта на острове Сокотра. Pripoda, 7.
Arias-Martínez, L., González-Reimers, E., Velasco-Vázquez, J., Santolaria-Fernández, F., & Hernández-Moreno, M. (2019). Auditory exostoses and their relationship to environmental factors in the pre-Hispanic Canary Islands. American Journal of Physical Anthropology. https://onlinelibrary.wiley.com/doi/abs/10.1002/ajpa.23757.
Barham, L., et al. (2023). Earliest Evidence of Structural Use of Wood at Kalambo Falls. Nature. https://www.nature.com/articles/s41586-023-06557-9.
Detroit, F., Mijares, A. S., Piper, P., Grün, R., Bellwood, P., Aubert, M., ... & Zeitoun, V. (2019). A new species of Homo from the Late Pleistocene of the Philippines. Nature, 568(7751), 181-186.
Morwood, M. J., Oosterzee, P. V., & Sutikna, T. (2007). The Discovery of the Hobbit: The Scientific Breakthrough that Changed the Face of Human History. Random House.
O'Connell, J. F., Allen, J., & Hawkes, K. (2010). Pleistocene Sahul and the Origins of Seafaring. Cambridge Archaeological Journal, 20(1), 69-84. doi:10.1017/S0959774310000055.
Strasser, T. F., Panagopoulou, E., Runnels, C. N., Murray, P. M., Thompson, N., Karkanas, P., ... & Coleman, J. (2010). Stone Age seafaring in the Mediterranean: evidence from the Plakias region for Lower Palaeolithic and Mesolithic habitation of Crete. Hesperia: The Journal of the American School of Classical Studies at Athens, 79(2), 145-190.
Trinkaus, E., Samsel, M., & Villotte, S. (2019). External auditory exostoses (Surfer's ear) in the human fossil record: A proxy for behavioral adaptations to aquatic resources. PLOS ONE, 14(8): e0220464. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0220464.
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