No / The DNA content of hair [1.] and [2.] is typically low compared to other tissues, as hair cells undergo dehydration and catabolic breakdown of nucleic acids and organelles during keratinisation [3]. As a consequence, ancient hair specimens have not been widely used as a source of ancient DNA. However, mitochondrial DNA (mtDNA) has been extracted from degraded and old hair samples, including burnt specimens [4], 100-year-old Native American samples [5], and wool from a 9,400 year old Bighorn sheep [6]. We have investigated the potential of hair as an aDNA source by analyzing DNA survival in 12 samples which range from 60 to >64,800 years of age and their susceptibility to contamination with modern DNA. mtDNA was successfully amplified, cloned, and sequenced from 10 of the 12 hair samples following decontamination procedures (Table 1). DNA was quantified using Quantitative Real-Time PCR in a subset of the samples (Table 1). The survival of high copy numbers of 16S DNA from the 3,000 year-old Pazyryk horse hairs is consistent with the observation that DNA survives longer at sub-zero temperatures [7]. Of greater surprise was the persistence of high numbers of 16S and Control Region DNA molecules in hairs sampled from a bison mummy 14C dated to >64,800 years. This result was independently replicated and extends the time frame from which authentic DNA has been retrieved from hair by at least seven-fold, placing it on a par with the oldest authentic DNA retrieved from bones and teeth [8]. No nuclear DNA could be amplified from the bison hair, consistent with observations of modern hair samples [1.] and 9. M.R. Wilson, D. Polanskey, J. Butler, J.A. DiZinno, J. Replogle and B. Budowle, Extraction, PCR amplification and sequencing of mitochondrial DNA from human hair shafts, Biotechniques 18 (1995), pp. 662¿669.[9.]. It is probably significant that the bison hairs are exceedingly well preserved ¿ the atomic carbon to nitrogen ratio (3.47) is similar to modern mammal hair [10.] and [11.] and histological analysis of the specimen demonstrates the only structural modifications to be slight cuticular loss and adherent deposits (Supplemental data).

A recent upsurge exists of archaeologists using ancient hair as a research tool, with new uses of this previously discarded archaeological material being introduced annually. Human hair deteriorates extremely slowly, and since the average modern human sheds approximately one hundred hairs per day, there should be copious amounts of hair debris left behind after humans leave a site; it is just a matter of how much of the hair survives in the archaeological environment. Most loose hair recovered from archaeological sites, however, is found fortuitously and in many cases, because archaeologists were not actively searching for ancient hair, it is possible they tainted the hair they later tested in ways that compromised their data, or more importantly contaminated their samples with modern hair and did not test ancient hair at all. No standardized method has previously been established for searching for ancient hair in an archaeological site. This paper considers (a) a method of soil extraction in the field that avoids contamination with modern hair and elements that might hinder later test data; (b) the processing of samples in the laboratory while continuing sample integrity; (c) identification of the types of soils and environments that are most favorable to hair preservation; and (d) an examination of the relevance of hair extraction from sites including the practicality and research potential. This paper examines five archaeological sites, using three different methods of hair extraction, examining the pros and cons of each. This should enable future researchers to find a method that works best for their particular site. It also analyzes the soil chemistry of the sites in order to study the soil and hair survival relationship, so that scientists can better determine which soils hold the best potential for hair survival. Laboratory methods that avoid contamination of the samples are also outlined in order to help researchers keep sample integrity after leaving the archaeological site.

A recent upsurge exists of archaeologists using ancient hair as a research tool, with new uses of this previously discarded archaeological material being introduced annually. Human hair deteriorates extremely slowly, and since the average modern human sheds approximately one hundred hairs per day, there should be copious amounts of hair debris left behind after humans leave a site; it is just a matter of how much of the hair survives in the archaeological environment. Most loose hair recovered from archaeological sites, however, is found fortuitously and in many cases, because archaeologists were not actively searching for ancient hair, it is possible they tainted the hair they later tested in ways that compromised their data, or more importantly contaminated their samples with modern hair and did not test ancient hair at all. No standardized method has previously been established for searching for ancient hair in an archaeological site. This paper considers (a) a method of soil extraction in the field that avoids contamination with modern hair and elements that might hinder later test data; (b) the processing of samples in the laboratory while continuing sample integrity; (c) identification of the types of soils and environments that are most favorable to hair preservation; and (d) an examination of the relevance of hair extraction from sites including the practicality and research potential. This paper examines five archaeological sites, using three different methods of hair extraction, examining the pros and cons of each. This should enable future researchers to find a method that works best for their particular site. It also analyzes the soil chemistry of the sites in order to study the soil and hair survival relationship, so that scientists can better determine which soils hold the best potential for hair survival. Laboratory methods that avoid contamination of the samples are also outlined in order to help researchers keep sample integrity after leaving the archaeological site.