A Tale of Two Diets
On the small Japanese island of Rebun, ancient garbage heaps tell a story of two neighboring cultures with surprisingly different diets. Archaeological sites like Hamanaka II contain stratified shell middens—layers of discarded shells and animal bones—that are a record of what people ate centuries ago. These remains show that the Okhotsk culture, which occupied the island from roughly the 5th to the 13th century AD, were intensely focused maritime hunters.
Zooarchaeological analysis of the bones from Okhotsk cultural layers reveals a diet of large sea mammals. Steller sea lions (Eumetopias jubatus) were a primary food source, alongside other pinnipeds like fur seals and various species of whales and porpoises. This specialization is so pronounced that sea mammal remains constitute the vast majority of the animal bones found at some sites. This dietary pattern points to a society with advanced open-water hunting technology, including specialized boats and toggle harpoons capable of taking such large, powerful prey. The Okhotsk people were coastal foragers and they were dedicated hunters of the open sea.
Neighbors with Different Menus
The dietary record preserved at Hamanaka II is notable because the site contains evidence of multiple, distinct cultures layered on top of one another. Before and after the Okhotsk, the island was inhabited by people of the Epi-Jomon and Satsumon cultures, who are considered ancestors of the historical Ainu. Their food waste tells a completely different story.
The faunal remains from Ainu-associated layers show a much greater reliance on fish, particularly salmon. While they also hunted terrestrial animals like deer, their diet did not feature the massive quantities of sea lion and seal seen with the Okhotsk. This difference in subsistence strategies between two groups living in the exact same environment is a puzzle. The Okhotsk, who migrated to the island from the north, brought a specialized sea-mammal hunting tradition with them. The Ainu maintained a more broad-based foraging and fishing economy with deep roots in the Japanese archipelago. For centuries, these two distinct cultures coexisted on a single small island, one looking to the open sea for giant mammals, the other turning to the rivers for salmon.