Sieving dirt is one of the activities that occurs on almost every archaeological site, whether it be large scale excavation or small scale like my own cremation urn study. The process involves putting all soil recovered from the excavation through a mesh wire screen. It improves the recovery rate of small artifacts and is an important step in archaeology. Screens can vary on size based on the dig or size of materials the archaeologist aims to find. This can change depending on the type of dig and the materials found. Sieving is a method also used on forensic sites to recover evidence that may be small or missed by human eyes.
In a new article by Mays, Vincent and Campbell (2012) explores the current process of sifting at mortuary sites and re-assesses the practice. Sieving the soil below the burial, while suggested, is often not a requirement. The authors note that “there is a dearth of empirical studies of recovery of human remains from archaeological sites which measure the effectiveness of sieving over handretrieval, or which compare the merits of using sieves of different mesh sizes”. The goal of their study is fulfill this gap and provide empirical data on the value of sieving, primarily in poorly preserved inhumation burials and loose teeth. They also assess the differences between hand collection and sieving, and the different size mesh screens.
The study was conducted during the excavations at the cemetery site of Whitby from 1999-2000. The cemetery was in use from the 7th to 9th century CE. The burials lacked grave goods, but the presence of coffin nails suggested that some of the individuals were interred in coffins. Due to the clay underlying the soil, preservation at the site was fairly poor leading to no wood surviving. This also caused poor preservation in the human remains; 325 graves were excavated but only 225 preserved any skeletal material. All remains recovered were highly fragmented.
The process for the sieving experiment involved removal of all grave fill by trowel to expose the skeleton. The burial was recorded and photographed, and then remains were removed by hand. Any soil remaining in the grave was then recovered in three samples for sieving and floatation. Sample A corresponded to the head area of the grave, sample B to the torso and sample C to the legs/feet area. All soil was wet sieved, a process involving gently washing the sieve and soil with water through a stack of sieves of decreasing mesh size (8mm, 4mm, and 2mm). Screens of 8 and 4mm were hand picked through for human remains, and 2mm was scanned. The samples found in the sieve were weighed separately in order to determine the success of the process, and they were scored by reliability of identifying the portions of bone (i.e. cranial versus axial versus dental).
Of the 70 burials that underwent this process, in 62 dental elements were found in the screening process and in 51 there were identifiable skeletal portions found in the screen. Skull fragments were identiﬁed in 43 burials, 34 had fragments of long-bones and 15 had fragments of other identiﬁable skeletal elements. Of the 62 burials with dental remains, a total of 946 permanent teeth were found, of which 913 (97%) were recovered during the sieving process. Overall, sieving increased the weight of the recovered human remains by 53% more than traditional hand collection alone.
While studying human remains is important, we need to remember that this is completely reliant on our ability to remove as much of the skeleton from the grave as possible, collecting all available evidence. Studies like this show that we need to be careful on the exhumation methods we are using, especially in the recovery of small elements such as dentition. It would also be important in sites that contained sub-adults who are more likely to have non-connecting small skeletal elements. Better methods in the field will lead to better interpretations in the lab.
S. Mays, S. Vincent, & G. Campbell (2012). The value of sieving of grave soil in the recovery of human remains: an experimental study of poorly preserved archaeological inhumations Journal of Archaeological Sciences DOI: 10.1016/j.jas.2012.05.006