Scientists have established quantitative dependences of the success of isolation and typing of ancient DNA on the content of organic carbon in bone tissue. This approach will help paleogeneticists around the world save time and resources by selecting only the most promising samples for expensive research.

Each of us is about 16 kilograms of carbon. It is this element that forms the basis of our cells, DNA and proteins. And when a person leaves, his bones remain in the ground, in which molecules remain — remnants of the very carbon from which life was once assembled. Extracting these molecules, "reading" them, and reconstructing the history of long—gone humans is the task of modern paleogenetics. But centuries later, it's not easy to figure out whether DNA has been preserved in ancient remains suitable for analysis.

According to scientists, working with ancient DNA is always a lottery. Over hundreds and thousands of years, nucleic acid molecules break down, fragment, and chemically modify. Even if the sample looks good, it does not guarantee that it has preserved the genetic material suitable for analysis. And each such analysis is a laborious and expensive process.

Scientists from the Southern Federal University, led by the staff of the UNC RAS, tested a method of preliminary "sorting" of archaeological samples, which allows predicting the success of the study with high probability. The study examined bone remains from burial mounds in the Rostov region dating back to the 7th–9th centuries and belonging to representatives of the Khazar Khaganate.

The researchers measured the total organic carbon (TOC) content in bone fragments and compared these indicators with the success of DNA isolation and subsequent genotyping. It turned out that the higher the content of organic carbon in the bone, the more likely it is to obtain a complete genetic profile.

"We found that the efficiency of PCR genotyping and the success of subsequent high-throughput sequencing directly correlate with the amount of organic carbon in the sample. If the CBT content is below 8 percent, the chances of success are minimal. Samples with an index of 8-9.9 percent can give results with standard PCR analysis, and for the most complex and expensive methods, such as NGS, it is better to take samples with a carbon content above 9.9 percent," said Igor Kornienko, Doctor of Biological Sciences, Associate Professor, head of the scientific laboratory "Identification of Objects of Biological Origin of the Southern Federal University".

Based on the data obtained, the scientists proposed a cost-effective strategy for selecting paleobiological material. It allows you to reject obviously unpromising samples at the earliest stage, without wasting time and reagents on their analysis. The analysis of organic carbon content takes only a few hours and is several times cheaper than a full cycle of DNA isolation and genotyping.

This approach is especially valuable for laboratories working with large archaeological collections. Instead of blindly conducting an expensive analysis of all available samples, researchers can first conduct a rapid assessment and focus on the most promising ones.

Today, the scale of paleogenetic projects in Russia has shifted from the study of single finds to the systematic analysis of entire necropolises, which requires sequencing hundreds and thousands of samples annually as part of the implementation of the Federal Scientific and Technical Program for the Development of Genetic Technologies. On the basis of the scientific laboratory "Identification of Objects of Biological Origin" of the Southern Federal University, these studies are conducted annually, implementing a full cycle of paleogenetic analysis — from laboratory DNA extraction from archaeological material to complex bioinformatic data processing. In the context of the Decade of Science and Technology (2022-2031), when Russian laboratories are faced with the task of mass genomic certification of ancient populations, our proposed express method for estimating total organic carbon acquires strategic importance. It allows cutting off up to 30-40% of obviously unpromising material at an early stage, which nationally saves millions of rubles of budget funds spent on expensive reagents for NGS sequencing, and significantly accelerates the acquisition of fundamental data on the genetic origin of the peoples of Russia.

How does the method work? The mechanics of the method are based on the search for a chemical "safety marker" inside the bone. The process begins with the preparation of a micronavesque — only about 0.5 grams of bone powder, which is placed in an automatic analyzer. The device performs a two-stage study: first, the sample is burned at a temperature of 680 ° C to measure the total amount of carbon (TC), and then the other part of the sample is treated with orthophosphoric acid. The acid reacts with the mineral component of the bone, releasing inorganic carbon (IC). The desired indicator, Total Organic Carbon (TOC), is calculated by simple subtraction: the mineral value is removed from the total value. The resulting figure is a kind of biological freshness index of the remains. Since DNA is part of the organic matrix of bone, a high TOC level directly indicates that the organic matter has not been destroyed over the centuries and the sample is highly likely to contain ancient DNA strands suitable for complex sequencing. Thus, the method makes it possible to assess the prospects of expensive genetic analysis by a chemical indicator before it begins. Thus, the method makes it possible to assess the prospects of expensive genetic analysis by a chemical indicator before it begins. And the NGS study proved this: samples with a high level of total organic carbon produced the maximum yield of ancient human DNA.

"The developed technique has already proved its effectiveness on the material of Khazar burial mounds. In the future, it may become a standard stage in the pre—processing of archaeological samples around the world, from preparation for paleogenetic research to the selection of materials for museum collections, where it is important to preserve valuable samples for future research," said Olga Aramova, PhD, Senior lecturer at the Department of Genetics at the SFedU Academy of Biology and Medicine.

The results of the study are presented in the scientific journal "Molecular Biology" in March 2026.