Archaeological Glycymeris glycymeris shells perforated at the umbo: Natural or man-made holes?

• Type: Article in International Scientific Journal
• Date: 2016

Authors

cabral, joão paulo s. (Author) FCUP

Journal

Title: Journal of Archaeological Science: Reports

Vol. 10

Pages: 474-482

ISSN: 2352-409X

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 5 Citations

Scopus - 7 Citations

Scientific classification

CORDIS: Natural sciences

FOS: Natural sciences

Other information

Authenticus ID: P-00N-DJM

DOI: 10.1016/j.jasrep.2016.11.008

Abstract (EN): The origin of perforations at the umbo of Glycymeris glycymeris shells found in Portuguese archaeological contexts, ranging from the Neolithic to the Middle Ages was approached in this paper through their comparison with similar perforations found in modern dead shells accumulated on beaches. This paper tries to establish simple criteria that can be used to distinguish between man-made holes at the umbo and those caused by natural processes of abrasion. Rough measures of shell abrasion were obtained as the ratio of preserved length of inner layer to the length of the shell, the degree of discolouration of the surface of the outer shell layer (measured by quantifying shell colour), the preservation of periostracum and of the ligament. It was found that presence of holes at the umbo was correlated with the higher values of all these measures of abrasion. The morphometric description of the perforations was achieved by measuring the four arms of the cross defined by the longest width and length of the hole. Measurements taken in 275 modern perforated shells were used to compute a system of principal components used to calculate the projections of the Portuguese archaeological specimens. These were found to be encompassed by the range of variability of the modern shell holes. It was concluded that the archaeological shells studied in the present paper have been collected at the seaside already perforated at the umbo, and that no human intervention is required to produce similar perforations of G. glycymeris shells found in archaeological contexts. One of the most distinctive features of the umbo perforation found in modern shells, which seems to be a good indicator of natural origin, was its flat baseline.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9