Developing radiocarbon dating of bone amino acids: refining chronology and resolving dietary and reservoir effects.
Lead Research Organisation:
University of Oxford
Department Name: Archaeology and History of Art Res Lab
Abstract
The carbon isotopes in protein that survives in archaeological human bone come from the food that was eaten, and so they record a basic vital aspect of our past struggle for existence. One isotope, radiocarbon, also enables us to measure the time since the food was eaten. An interesting complication arises when the food is from the sea, or from rivers or lakes. In such cases, radiocarbon dates are often erroneously old due to 'radiocarbon reservoirs' arising from geochemical effects between the atmosphere and the organisms being eaten. We have developed a method which is able to dissect this complication, and use it to unravel both the error in the dating, and to estimate the extent to which such aquatic resources were being consumed. Our method is able to measure individual components (amino acids) in the protein, and compare those which are known to have different dietary origins (i.e. the essential and non-essential amino acids). In this research we aim to develop the laboratory method to a fully robust state, and then test it over a range of suitable applications, where dates or diets are in question. This new method will enable the radiocarbon dating of human remains to be made more accurately, since the effects of radiocarbon reservoirs can be detected and avoided. At the same time, it can provide definitive evidence, which can be quantified, for freshwater fish consumption. Our project here builds the foundation for such a study in Europe. The eventual goal is to understand the role of freshwater fish consumption during the transition to farming that swept across Europe some 8000 years ago. Rather little is known about the continuation of fishing, even though rivers were important for migration and settlement, because the evidence has been hard to obtain. It seems that fishing probably ceased in some areas (as also with sea-fishing) but continued in others. This new methodology will sharpen the chronology, and the understanding of subsistence, of how rapidly the Neolithic way of life took root across Europe. We make a start by addressing the best studied area of the Danube Basin.
Organisations
Publications
Higham T
(2010)
Chronology of the Grotte du Renne (France) and implications for the context of ornaments and human remains within the Châtelperronian.
in Proceedings of the National Academy of Sciences of the United States of America
Marom A
(2012)
Single amino acid radiocarbon dating of Upper Paleolithic modern humans.
in Proceedings of the National Academy of Sciences of the United States of America
Nalawade-Chavan S
(2014)
New hydroxyproline radiocarbon dates from Sungir, Russia, confirm early Mid Upper Palaeolithic burials in Eurasia.
in PloS one
Nalawade-Chavan S
(2014)
New single amino acid hydroxyproline radiocarbon dates for two problematic American Mastodon fossils from Alaska
in Quaternary Geochronology
Nalawade-Chavan S
(2016)
Compound-Specific Radiocarbon Dating of Essential and Non-Essential Amino Acids: Towards Determination of Dietary Reservoir Effects in Humans
in Radiocarbon
Zazula GD
(2014)
American mastodon extirpation in the Arctic and Subarctic predates human colonization and terminal Pleistocene climate change.
in Proceedings of the National Academy of Sciences of the United States of America
| Description | Our research has developed a novel method that allows us to provide radiocarbon dates from bone amino acids that are free of contaminants. In archaeology dating is extremely important, without a reliable chronology comparisons between regions fall apart and one is not able to be confident about issues of contemporaneity and timing. Bones may become contaminated at several steps; from ground acids in the archaeological sediment in which they are excavated to the museum where they are conserved with glues, consolidants and resins. Failure to remove these prior to the dating process may result in dates that are erroneous. Using routine cleaning methods we have shown that badly contaminated bones may not be cleaned to the level required to produce accurate dates. In some instances we not dates that are thousands of years too young. Our work, however, has succeeded in developing a method by which a compound specific only to the bone can be extracted and dated, thereby eliminating the contamination issue. We have developed a method of extracting the amino acid hydroxyproline, which is more or less a biomarker for mammalian collagen, and rarely if ever found outside this substance. A date on hydroxyproline is a 'gold standard' measurement, free of contaminants. We have shown this with respect to several highly contaminated bones from Europe and North America. We have also developed methods that allow us to extract and date other amino acids, some of which are essential (cannot be synthesised in the body) and other non-essential (can be synthesised). We have used this approach to explore dietary adaptations in humans living in the Mesolithic and Neolithic period of Europe. Humans eating marine and freshwater resources will often have a diluted radiocarbon concentration because of the fact that fish living in the sea and in rivers have a lower amount of radiocarbon in them. Humans eating fish can date too old for this reason. By selecting essential amino acids for dating, we have shown the offsets that are might accrue and by dating non-essential amino acids we hoped that we could obtain dates that are more reliable and may be derived from non-reservoir carbon sources such as plant carbohydrates. The results of this work were mixed and we are still undertaking research on this aspect of the science. |
| Exploitation Route | We are still working on aspects of the research. One of our team (Higham) obtained an ERC grant and a postdoctoral researcher on this grant (Dr Thibaut Deviése) is working on extending the amino acid preparative method, testing new columns and other aspects of the chemistry method for dating bones that are low in collagen. Some of the results are in the process of being published. We are committed to making the method faster and more efficient (at the moment only one sample a day can be prepared ) and have applied for an ERC Proof of Concept grant to achieve this. |
| Sectors | Agriculture, Food and Drink,Culture, Heritage, Museums and Collections |
| Description | Only very generally, inasmuch as the ultimate research aim of archaeological science (of which this project is a part) is to develop a more detailed and reliable account of human history. A basic part of that account is to have a timeline for major human developments, which entails have the ability to date key event in human history. This work both helps to improve dating, particularly in the critical "emergence of Modern Man" period, and it also helps to provide insight into the basic diets of humans at that time in various locations. |
| First Year Of Impact | 2015 |
| Sector | Culture, Heritage, Museums and Collections |
| Impact Types | Cultural,Societal |
| Description | ERC Advanced Grant |
| Amount | € 2,490,000 (EUR) |
| Organisation | European Research Council (ERC) |
| Sector | Public |
| Country | Belgium |
| Start | 05/2013 |
| End | 05/2019 |
| Title | Radiocarbon dating single amino acids using HPLC |
| Description | Our team developed novel methods for separating amino acids from bone using Preparative High Performance Liquid Chromatography (Prep-HPLC) in order to a) improved chronometric applications of radiocarbon dating to archaeological bones and; b) to explore dietary adaptations of the human past and improve the dating of non-essential and essential amino acids to determine whether the former could provide more reliable age estimates. Until recently, work on the former has focused on single amino acid dating mainly focused on isolating and dating hydroxyproline. This approach has shown to be very efficient in the dating of bones that are extremely contaminated with soil contaminants as well as preservative materials applied during and after archaeological excavation. This method also allows us to separate and analyse essential and non-essential amino acids. In the direct AMS dating of omnivorous human remains this might allow us to select amino acids that are less affected by radiocarbon reservoir offsets. The chromatography method is time consuming which has so far prevented its adoption as a routine technique for isolating amino acids for radiocarbon dating. It has only been used in a limited number of cases for bone samples which have high levels of contamination that could not be removed by other methods. In our research programme, we developed several novel approaches to the amino acid dating method designed to; a) reduce the sample preparation without increasing the risk of contamination b) radiocarbon date samples that are heavily contaminated; and; c) date bone samples with very poor preservation of collagen. We managed to develop a method that uses water as the mobile phase within the HPLC and reduced the background carbon measured on the columns to very low levels, monitoring the column bleed to ensure this was minimised and quantified, hence allowing a correction to be made. We developed a protocol to ensure reliable and accurate AMS dates from hydroxyproline, and also extracted a range of amino acids derived from essential and non-essential sources to explore palaeodiet in humans from the Mesolithic and Neolithic period. These developments have been reported in the literature given in the Publications section of this report. |
| Type Of Material | Improvements to research infrastructure |
| Provided To Others? | No |
| Impact | Dating early anatomically modern humans reliably from sites in Russia and Europe, in many cases for the first time, due to contamination that has been impossible previously to remove. |
| Description | Conferences |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Conference presentations at the 2011 Radiocarbon Conference, the 2012 C14 and Archaeology Conference and the 2014 Gravettian hunters conference (Cracow). |
| Year(s) Of Engagement Activity | 2011,2012,2014 |