Rats and other rodents and pests can make great archivists.

That’s because they forage food and build dens, storing fabric, paper, animal bones, plant remains and other materials under floorboards, behind walls and in attics, crawl spaces and wells. There, these materials might dry out and remain undisturbed for hundreds of years.

By analyzing the materials in these nests, archaeologists like me can learn more about the people who once lived nearby.

I studied a rat nest that was used by generations of rats over several decades and was found under the floorboards in the attic of the historic home at Bartram’s Garden in southwest Philadelphia. In 1728, Quaker farmer and naturalist John Bartram began to plant his garden, which is considered the oldest botanic garden in North America. I studied thousands of plants collected by rats and learned how the........

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