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The Part We Play in—Not Just on—Our Environment

A study of ancient inhabitants of Sanak Island, Alaska, points to a new understanding of our impact on the natural world.
Sanak Peak from the northern side of Sanak Island. (Photo: Wikimedia Commons)

Sanak Peak from the northern side of Sanak Island. (Photo: Wikimedia Commons)

Where do humans fit in our ecosystems, and what can we do to preserve humanity for the future? It's a complex question to say the least, but a new study of the ancient occupants of Sanak Island in Alaska's Aleutian Islands suggests some lessons for modern humans—notably, vary what you eat, and avoid stuffing your faces with the rarest, most exotic plants and animals.

The study, authored by Santa Fe Institute Professor Jennifer Dunne and researchers from seven other institutions, is one of the first—and so far the largest—to look at the integral part humans play in their food webs, the complex networks that describe what eats what in a natural ecosystem. Though no one lives there anymore, Sanak Island was a perfect place to study because of its extraordinarily long history—humans first settled the island 10,000 years ago and stayed until the 1960s, when the last Aleut people left for mainland Alaska.

On the other hand, studying thousands of years of human ecological history on the island is no easy task. To get the whole picture, Dunne says, required combining a wide range of information. Ecologists, for example, gathered information on modern food webs on the beaches of Sanak Island as well as in the surrounding oceans, while archaeologists studied ancient middens—trash heaps, basically—for clues to what early island occupants ate. Anthropologists interviewed Aleut elders for a clearer understanding of not only what people on the island ate, but also how they decided what to eat.

Avoid stuffing your faces with the rarest, most exotic plants and animals.

Taken together, the researchers learned that Sanak Island occupants were "supergeneralists ... and really omnivorous," Dunne says, meaning that they ate everything from algae to sea lions and sharks, and one quarter of the plant and animal species available to them. Perhaps more importantly, they engaged in a practice called prey switching. "When the weather was really awesome, they'd go out in their kayaks and hunt" marine life, but when the weather was bad, they'd stick to gathering shellfish and other food sources near the shoreline. And when one species's population began to decline, Sanak Islanders would simply hunt or gather something else.

Computer simulations and observations from other food webs suggest that prey switching makes for a healthier ecosystems, which helps explain why there's no evidence of extinctions on and around Sanak Island despite the islanders' relatively sophisticated hunting technology, Dunne says.

That stands in stark contrast to how we consume some marine life, such as blue fin tuna, today. Though the fish is increasingly rare and sells for $100 a pound (wholesale), that only seems to be increasing demand. Humans, Dunne says, aren't prey switching, and that could have serious consequences for blue fin tuna and throughout the oceans' food webs.

The study is the first component of a larger effort to better understand both prehistoric and modern humans' role in their ecosystems, as opposed to the impact humans have on their ecosystems, Dunne says, "[giving] us a new way to understand our impact" on the natural world.


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