A new miniSTR heptaplex system for genetic fingerprinting of ancient DNA from archaeological human bone

The analysis of short tandem repeats (STRs) is a useful tool in various contexts of ancient DNA research. Main applications are the reconstruction of kinship, identification, and authentication. Here we describe a short amplicon autosomal short tandem repeat (miniSTR) heptaplex system for the amplification of D13S317, D21S11, D18S51, TH01, D5S818, FGA and Amelogenin from highly degraded DNA as an inexpensive alternative to commercially available kits. All primers were newly designed and the amplicon length of all systems is less than 200 bp, with the exception of some rare alleles in the FGA and D21S11 systems. To validate the suitability of this system for typing STRs from human specimens with low DNA preservation we systematically tested it on 20 skeletal samples from four archaeological sites representing different burial environments and time spans since death. Finally, to test the sensitivity of the heptaplex system, we analyzed serial dilutions of control DNA and ancient DNA extracts. Using the system we were able to reproducibly obtain full STR profiles, down to a concentration of 0.06 ng DNA. Even with 0.004 ng DNA partial profiles could be amplified. The accumulated power of discrimination for the six selected STR loci is 0.99999984, plus the option of genetic sex determination through Amelogenin. The tests conducted prove that the system presented is efficient and especially suited for cases where STRs have to be typed and sex has to be assessed from human specimens with highly degraded DNA.     

Insights from a tribological analysis of the tribulum

Since the 1980s, “strange” microwear traces were found to occur on flint blades from sites in the Near East from the late Neolithic and occurring in great abundance by the Early Bronze Age. Although these were considered by archaeologists to be sickles because they had visible gloss on their edges, their use-traces could not be reproduced in harvesting experiments carried out in the field. Subsequently, several lines of evidence were used to study the blades, including not only direct observation of microscopic wear traces, but also Near Eastern cuneiform texts from the third and second millennium BC describing agricultural instruments and analogy with ethnographic and experimental reference material. We found that these tools and their traces best matched traces on flint used to arm the underside of a tribulum (threshing sledge) for threshing grain and cutting straw. We built a replica of the tribulum described in cuneiform texts from the Bronze Age, using copies of the Bronze Age blades, and used this instrument in experiments.