Compound specific radio carbon dating accuracy


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Radiocarbon




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Aaccuracy specific dating is not new. It specufic existed — at least in theory — since the s, but Compoind recently had never been totally successful. Aaccuracy techniques had been tried, but none were hugely effective. While still in its early days, the current method to isolate and date specific compounds is proving reliable and accurate. In order to isolate a specific biomarker, the sample has to undergo more pre-treatment steps than normal — and, as a rule, the more steps added to a technique the more room there is for error and the more diligent laboratory technicians need to be. It also means that the procedure is costly and time-consuming: As such, ORAU is primarily using the technique on samples that are not amenable to standard dating methods, such as those that have a high degree of contamination either from the burial environment or from museum conservation work; Palaeolithic bone samples are usually the most affected by such problems.

Vindija Cave, Croatia, home to Neanderthal remains. Neanderthal remains discovered in the cave were originally thought to be of significant archaeological importance, as radiocarbon dates from the bones suggested that Neanderthals may have inhabited the region as recently as 28, BP.

This date speicfic have meant that carhon co-existed with anatomically modern humans, and might have actually produced some of the Upper Palaeolithic artefacts normally attributed to Homo sapiens. Subsequent redating of the Datibg samples in the mids produced a slightly older date of 33, BP — which still kept the possibility of an overlap with modern humans. The dates found using the compound specific technique, however, revealed that the Neanderthal remains were actually even older, from before 40, BP, and so probably pre-dated the arrival of modern humans in the region. It is, so far, the only Pleistocene human fossil found in the country.

Subsequent investigations around the find-spot did not yield additional fossil remains. The skullcap has a mostly complete frontal as well as two partially complete parietal and nasal bones. Ages suggested for the specimen range from the Early Middle Pleistocene to the terminal Late Pleistocene. The presence of archaic features has led to a potential affiliation to an uncharacterized archaic hominin species.

Radio dating specific Compound accuracy carbon

The specimen was thus initially referred to as Mongolanthropus 6. The comparison of the dimensions of the skullcap with reference skullcaps by multidimensional Compoynd analysis showed similarities with Neanderthals, Homo erectus and Asian archaic Homo sapiens 7. Based on the published photographs, Kaifu and Fujita 8 suggested that the Salkhit specimen belongs to a terminal Pleistocene modern human. Additional comparisons with Datinh and Late Pleistocene hominin fossils from northeast Asia Zhoukoudian Locality 1, Dali, and Zhoukoudian Upper Cave concluded that the peculiar features of the Salkhit skull are more likely to be regionally predominant modern human epecific than diagnostic features of sprcific archaic species 9 Because of the dearth of hominin fossils recovered in Mongolia, the Salkhit skull represents a unique opportunity to investigate the types of humans that occupied the region during the Pleistocene.

Here, we present the results of both chronometric and genetic analyses of the Salkhit specimen. This fossil dates to approximately 34—35 thousand years ago and its mitochondrial genome is of Eurasian modern human type. Results and Discussion Fossil specimen Since its discovery inthe Salkhit fossil Reference number: In norma frontalis 1in norma basilaris showing the first sampling for dating A 2 and the areas of sampling B, C, D and E 3 for genetic analyses and compound-specific radiocarbon dating. Unfortunately, no information is available about the sample preparation methods that had been applied. The C: N atomic ratio of carbon to nitrogen for the extracted collagen was 3.

Even though this value falls within a range of C: N values [2. We therefore decided to re-date the skullcap using a compound-specific approach The higher efficiency of this method in removing contaminants from heavily contaminated samples and its ability to provide accurate 14C measurements has been demonstrated in several recent cases involving Paleolithic sites in France 14Croatia 15Russia 161718192021and the Americas 22 A new bone sample was obtained and after extraction, the collagen was hydrolyzed and the amino acid hydroxyproline was isolated using preparative High Performance Liquid Chromatography Prep-HPLC.

N atomic ratio measured was 5. The date were calibrated using OxCal 4. This is significantly older than the two dates obtained previously. Such differences have been observed before in cases where bones were heavily contaminated with conservation agents, indicating that the standard chemical pretreatment 12 is sometimes not efficient enough to remove all high molecular-weight contamination that is present in a sample and sometimes even cross-linked to the collagen.

Yi, S. And of the dearth of hominin characterizations tracked accuarcy Mongolia, the Salkhit alexander represents a unique super to weigh the factories of humans that virtual the dividend during the Area. The wind of estimators that occurred in the Salkhit mtDNA since its loyalty from the height of haplogroup N was updated by only parsimony thread using mtPhyl.

They revealed the presence of a silicone-based contaminant in the Salkhit bone probably used to make the endocast Fig. The hydrolysis of the collagen and isolation of the amino acid hydroxyproline obviated this problem. Table 1 Radiocarbon dates of the Salkhit skull Full size table Fig. Figure produced using OxCal 24 Full size image Fig. The profile of the Salkhit sample also shows the presence of 3 compounds with siloxane structure red arrows that are reported as pyrolysis products of silicone 53 leading to assess the residual presence of such material within the bone matrix Full size image DNA extraction and mtDNA enrichment DNA was extracted from Aliquots of the extracts were converted to single-stranded libraries 27 and enriched for human mtDNA fragments using a present-day human mtDNA probe set The enriched library molecules were sequenced from both ends.

Overlapping paired-end reads were merged to reconstruct full-length molecules sequences, which were then mapped to the revised Cambridge reference sequence of the human mitochondrial genome rCRS, GenBank acc. Table 2 Characteristics of the mtDNA molecules isolated from the Salkhit skullcap Full size table To assess whether or not molecules of ancient origin were present, we estimated the frequencies of cytosine C to thymine T mismatches along the sequences relative to the reference sequence. Such mismatches result from deamination of C residues in ancient DNA, particularly towards the ends of molecules The C to T mismatch frequencies ranged from The differences among the libraries suggest that, in addition to endogenous ancient DNA molecules, contaminating present-day human mtDNA molecules were extracted and incorporated in the libraries.

We conclude that the DNA libraries contain authentic ancient molecules carrying terminal C to T mismatches as well as present-day contaminating DNA molecules. The estimation of present-day human contamination in each library relied on two positions pos.

The proportions of sequences covering both positions and not matching the Salkhit-specific state are Because of the high level of contamination of the specimen, we called the Rado mtDNA consensus using only the 38, mtDNA fragments carrying C to T mismatches to radoo human reference mtDNA in one specifkc their three first or three last positions recovered from the three DNA speicfic. This significantly lowers the amount of modern human contaminating sequences and reduces Cimpound potential bias for contaminating molecules resulting from the use of modern human capture baits and reference sequence for mapping.

One of the two missing positions was in a C-homopolymer stretch pos. This observation might reflect heteroplasmy and was left uncalled. For the alignments of deaminated fragments only, we estimated the level of contamination to 4. Given the coverage of the genome, this level of contamination is not expected to affect the accuracy of the consensus sequence. While the mosaic of archaic-like and modern human-like morphological traits have made the assignment of the fossil to Pleistocene hominin groups difficult, we thus show that the mtDNA of the Salkhit individual is of modern human origin.

However, the sequence does not carry any substitutions characteristic of known sub-haplogroups inside the haplogroup N. A maximum parsimony analysis subtree Fig. It is therefore unlikely that the Salkhit mitochondrial lineage is directly ancestral to any present-day human mtDNA.


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