food sources in the stream. Thompson and Pluckhahn conclude that the mortuary mound and pond complex was built much earlier. They agree that only a few families lived permanently on the site, but they found evidence of a larger number of people living there probably during times of construction. Such alterations to the physical landscape at Fort Center for continuous for almost twenty-five centuries. this would necessitate a volunteer labor force living periodically onsite. The regular group funerals would require lodging for the families of the deceased. Circular ditches Sears' team of archaeologists found three circular ditches at Fort Center. Two were about 300 feet in diameter, and partially overlapped. A third, later circular ditch was about 1,200 in diameter. It enclosed the earlier ditches, but was not concentric with either of them. This ditch was 25 to 30 feet wide, and six feet deep. Most of the dirt from the ditch had been thrown on the inner side of the ditch. There were two gaps in the ditch, one on the southeast side and another on the east side, closest to Mound B in the Ceremonial Complex. No artifacts were found in the ditches or in the area enclosed by the ditches, but maize pollen was found under soil that had been disturbed from digging the ditches. Radio-carbon dating indicates that all three circles were complete by 450 BCE. There is no evidence of the circles being used for habitation, ceremonial or defense purposes. Sears holds that the maize pollen indicates that the circles were used for cultivation. The ditches around the circles penetrated the hardpan, helping to drain the prairie soil. Sears also states that the Great Circle likely was used for gardens from several centuries BCE until the end of period II, around 600 to 800. Sears compares the circular ditches at Fort Center to similar circular ditches used for agriculture in pre-Columbian Colombia. Sears states that the circles at Fort Center were earlier than those of the Adena culture of the Ohio River valley. Sears believes that the Fort Center circles are related to circles at Hopewellian sites. He states that circle earthworks were almost certainly imported into Florida from South America along with maize. Sears believes that the inhabitants of Fort Center, who dug the circular ditches and introduced maize and cord-tempered pottery to the area, were people who were descended from migrants from South