Abstract
Current protocols for ancient DNA and radiocarbon analysis of ancient bones and teeth call for multiple destructive samplings of a given specimen, thereby increasing the extent of undesirable damage to precious archaeological material. Here we present a method that makes it possible to obtain both ancient DNA sequences and radiocarbon dates from the same sample material. This is achieved by releasing DNA from the bone matrix through incubation with either EDTA or phosphate buffer prior to complete demineralization and collagen extraction utilizing the acid-base-acid-gelatinization and ultrafiltration procedure established in most radiocarbon dating laboratories. Using a set of 12 bones of different ages and preservation conditions we demonstrate that on average 89% of the DNA can be released from sample powder with minimal, or 38% without any, detectable collagen loss. We also detect no skews in radiocarbon dates compared to untreated samples. Given the different material demands for radiocarbon dating (500 mg of bone/dentine) and DNA analysis (10–100 mg), combined DNA and collagen extraction not only streamlines the sampling process but also drastically increases the amount of DNA that can be recovered from limited sample material.
Highlights
Over the past 70 years, radiocarbon dating has become an important tool for archaeology due to its precision in dating organic material up to approx. 50,000 years in age
To determine whether it is feasible in principle to extract DNA and collagen from the same sample material without affecting radiocarbon dates, we used a dentistry drill to remove 7 g of powder from a 300-year-old horse bone close in age to the upper limit of radiocarbon dating, and 8 g of powder from a >50,000-year-old cave bear bone (“background bone”, sample B) containing no detectable endogenous 14C isotopes
Following DNA release, half of the aliquots were used for collagen extraction and dating, and half were incubated with an ethylenediaminetetraacetic acid (EDTA)/proteinase K buffer commonly used in ancient DNA extraction to achieve full lysis of the bone powder and release any residual DNA
Summary
Over the past 70 years, radiocarbon dating has become an important tool for archaeology due to its precision in dating organic material up to approx. 50,000 years in age. Useful genetic data was retrieved from extremely small amounts of less well-preserved material[12,13,14], most recently from as little as 10 mg of powder removed from a milk tooth discovered at the site, which was shown to belong to a Denisovan individual based on the analysis of 1 million base pairs of its nuclear genome[15] Both destructive methods, DNA analysis and radiocarbon dating, are invaluable tools for reconstructing past events and their timing, such as the colonization of Europe by anatomically modern humans (AMH) and Neanderthal extinction[7,16,17,18]. Since carbon contamination may arise from organic molecules that have entered the bone or tooth matrix through soil detritus, microbial invasion or post-excavation handling, ABA-gelatinization is often followed by ultrafiltration through membranes that separate high molecular weight collagen chains from shorter peptides, amino acids and other small molecules[3,21]
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