Single amino acid radiocarbon dating of Upper Paleolithic modern humans

Abstract

Archaeological bones are usually dated by radiocarbon measurement of extracted collagen. However, low collagen content, contamination from the burial environment, or museum conservation work, such as addition of glues, preservatives, and fumigants to "protect" archaeological materials, have previously led to inaccurate dates. These inaccuracies in turn frustrate the development of archaeological chronologies and, in the Paleolithic, blur the dating of such key events as the dispersal of anatomically modern humans. Here we describe a method to date hydroxyproline found in collagen (∼10% of collagen carbon) as a bone-specific biomarker that removes impurities, thereby improving dating accuracy and confidence. This method is applied to two important sites in Russia and allows us to report the earliest direct ages for the presence of anatomically modern humans on the Russian Plain. These dates contribute considerably to our understanding of the emergence of the Mid-Upper Paleolithic and the complex suite of burial behaviors that begin to appear during this period.HPLC | accelerator mass spectrometry | Kostenki | Sungir

Chronology of Late Pleistocene Humans in Eurasia: Results and Perspectives

“…If we take into account the 14 C dates of-21,800-22,500 BP run on charcoal collected beneath the Sungir 1 skeleton (see Kuzmin et al 2004:733), the youngest value (AA-36473) is the most reliable one. As for the double burial of the Sungir 2 and 3 individuals, the new 14 C date of-26,000 BP for Sungir 3 (Dobrovolskaya et al 2012; The latest 14 C dates of the Sungir 2 and 3 individuals (Marom et al 2012) are older than the other values (see Table 1). Although Marom et al (2012) are convinced that the dating of hydroxyproline amino acid of collagen from these skeletons gives the most reliable ages, the situation, in our opinion, is not as simple as that.…”

“…As for the double burial of the Sungir 2 and 3 individuals, the new 14 C date of-26,000 BP for Sungir 3 (Dobrovolskaya et al 2012; The latest 14 C dates of the Sungir 2 and 3 individuals (Marom et al 2012) are older than the other values (see Table 1). Although Marom et al (2012) are convinced that the dating of hydroxyproline amino acid of collagen from these skeletons gives the most reliable ages, the situation, in our opinion, is not as simple as that. Without knowledge of the true age for the Sungir 2 and 3 burials, it is impossible to prove that some compounds in bone collagen are more resistant against contamination or degradation.…”

“…The age of the Kostenki 18 individual is much younger, -21,000 BP (Table 1); due to the absence of a stratigraphie connection between these 2 directly dated humans, it is impossible to evaluate the age difference. The recently dated Kostenki 14 individual is the oldest at -33,250 BP (Marom et al 2012; see Table 1). …”

The curious case of the Arctic mastodons

“…However, interestingly even with the use of ultrafiltration, several fossils still appear sufficiently young to give the impression that mastodons were present around the time of the last glacial maximum. For these last few specimens Zazula et al (3) use a more involved separation to isolate the single amino acid hydroxyproline, a bone-specific biomarker that is highly specific to bone protein collagen and, hence, unlikely to represent exogenous contamination (14). This approach proved the remaining "young" mastodon specimens as being either near or beyond background detection limits, in keeping with the population of redated specimens.…”

“…Because these contaminants may be sourced from the environment and not the organism, they may be of a different (and typically younger) age, so their removal is critical to determine an accurate date. This aspect is particularly true for fossils beyond a few half-lives in age (one 14 C half-life = 5,730 y), for which even a small amount of contamination with younger carbon can make an old fossil date appear tens of thousands of years younger than it is. Zazula et al's (3) use of this protocol when applied to dating the "young" mastodons from the Arctic, demonstrates that most of these fossils are in fact beyond the practical limit of radiocarbon dating (>∼50,000 y).…”