What can a handful of old oyster shells reveal about the trials some of the New World's early European settlers? A lot, it turns out.

As a prevalent resource in the Chesapeake Bay, eastern oysters (Crassostrea virginica) ended up being a crucial food source for the first full-time European settlers in North America, who arrived in 1607, the second year of a seven-year drought that was the worst the region had seen in some 800 years.

The struggles of these early settlers is well documented, and estimates of fatalities during the harsh winter of 1609 to 1610 hover around 44 percent of the total population, with starvation and lack of fresh water being among the primary causes of death. But aside from written records, there have been few ways to assess the specific climatic conditions of the first few tough years of the settlement.

Like most people living in the U.S. today, Jamestown settlers tossed the oyster shells out as garbage after they were through with the insides. Despite careless discarding, "the environmental and ecological data recorded in the [shell growth] remained intact over the centuries," noted the authors of a new study, published online May 31 in Proceedings of the National Academy of Sciences. This biological record provides "a unique window into conditions during the earliest Jamestown years."

In 2006, archeologists uncovered a previously unknown well in the settlement area that had been dug sometime after 1609 and then filled in and closed off before 1617. And luckily for the research team, led by Juliana Harding, of the Department of Fisheries Science at the College of William and Mary, much of the well's garbage fill turned out to be old oyster shells.

By analyzing the oxygen isotopes in the 17th-century shells and comparing them to those from the modern James River, the researchers were able to ascertain the severity of the drought during which the oysters had been harvested (between the fall of 1611 and the summer of 1612). The oyster shell data also revealed that the James River was much saltier during the settlers' time than it is today. Although this would have made it more difficult for the settlers to find fresh river water to drink, it also brought the oyster populations farther upstream and closer to the settlement. Despite this convenient supply, shell analysis also showed that settlers were augmenting their oyster supply from stocks closer to the Chesapeake Bay.

Although in the U.S. today, oysters are often considered fine dining, few might pause over a chilled platter of these bumpy bivalves to think that, as the authors wrote, "survival of the first permanent English settlement in North America would be intimately linked to local oyster populations."

Image of ancient fossilized Crassostrea virginica (not used in the study) courtesy of Wikimedia Commons/Kevmin