Scientists have found traces of a forgotten city that existed 700 years before Alexander the Great founded Alexandria as part of his efforts to conquer the known world.
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While studying Greek and Roman ruins in the waters around the Egyptian city, Jean-Daniel Stanley of the Smithsonian Institution's National Museum of Natural History and his colleagues discovered evidence of building construction that was much older than they had expected.
"It was serendipitous that what we found dates pre-Alexander," says Stanley, whose findings have been published in the August issue of the journal GSA Today. "We thought that there was a city, but you need to have something in hand. We have the first part of it. We have the timing."
Historians have generally agreed that some settlement—a modest fishing village, a more substantial walled center or possibly a fortified settlement—referred to in ancient histories as Rhakotis existed here centuries before Alexander arrived. But until this discovery, they lacked physical evidence.
In 2001, Stanley, working with a team of geologists, anthropologists and geochemists, collected seven underwater sediment core samples measuring three inches wide, 6 to 18 feet long and up to 20 feet underwater from sites scattered across Alexandria's nearly square-mile East Harbor.
The intent of the study had been to look at how catastrophic and human events contribute to cities submerging, and to apply the findings to cities like New Orleans and Venice. But, as Stanley and his colleagues have now confirmed, they ended up finding five critical indicators of human activity, including ceramics; rock fragments derived from Middle and Upper Egypt; and significant amounts of lead, heavy minerals and organic matter, dating back to 1,000 B.C.
Four years later, Stanley and his colleagues embarked on a more systematic study to confirm his discovery of the buried settlement, analyzing the sediment through archaeological, stratigraphical, petrological and geochemical methods. Among other tests, the researchers compared the site's ceramic fragments with those typical of the southeastern Mediterranean in the ninth to seventh centuries B.C. On average, Stanley found three to four traces of human activity in each sediment core.
"Looking at any one indicator [of human activity], you could find an explanation," Stanley says. "But the fact that you have five independent parameters—that's very robust evidence. I'd say it's a safe bet."
Typically, the top two layers of sand and mud in cores from East Harbor and mainland Alexandria contain pottery fragments, high concentrations of heavy minerals, organic waste, lead, quartz and crystalline and limestone, because these layers correspond to the era of rapid municipal development that occurred during the reign of the Ptolemies and Romans. Heavy construction, metallurgic activity and sewage runoff account for these remnants.
Until now, however, similar indicators had not been found in layers dated to pre-Greek times. Stanley and his colleagues extracted pottery fragments from locally produced cooking containers, heavy minerals and organic matter—all from sediment radiocarbon-dated back to seven centuries before 332 B.C.