Rat Bones Reveal How Humans Transformed Their Island Environments

Smithsonian ^ | June 6, 2018 | Lorraine Boissoneault

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For the Polynesian islands, that meant the arrival of agricultural crops like breadfruit, yams and taro, as well as domesticated animals like dogs, pigs and chicken. The early settlers also used slash-and-burn agriculture to remove forests and fertilize the soil and likely hunted many seabirds to extinction.

To get a more precise view of how human behavior impacted the islands, Swift and her colleagues used stable isotope analysis. Carbon analysis is based on the way plants process carbon dioxide: most agricultural products are classified as C3 plants, while tropical grasses are usually C4 plants. If rat bones show a higher level of C3 than C4, they were probably sneaking off with human tidbits like sweet potato and taro. Then there’s the nitrogen isotope, which increases as you move up the food chain (e.g. lions have higher nitrogen isotope levels than antelopes).

In the case of the Polynesian islands, higher nitrogen isotopes usually correlated with marine food sources, because the marine food web has a longer chain of predators eating other predators. That meant if the rats showed high nitrogen isotopes, they were feasting on seabirds, fish or other marine treats.

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Painting of four species of rat, including the Polynesian rat (right). (National Geographic Creative / Alamy)

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Ancient agricultural activity caused lasting environmental changes
Eurekalert | June 13, 2018 | U of British Columbia
Posted on 06/19/2018 9:14:11 PM PDT by SunkenCiv
http://www.freerepublic.com/focus/chat/3664570/posts