The discovery of ancient DNA (aDNA) extracted from petroleum samples has revolutionized our understanding of the preservation of genetic material and its implications for studying the evolution of life on Earth.
A research team successfully isolated over three million fragments of DNA from oil samples using innovative nanoparticle-based technology. Their analysis revealed surprising information about extinct species and geological events that have shaped the planet. This study raises new questions about the capacity of oil to preserve genetic material over millions of years and challenges previous criteria regarding the authenticity of ancient DNA. The findings were published on bioRxiv, a preprint platform where researchers share studies prior to formal peer review, indicating that results should be interpreted with caution until validated by other experts.
Traditionally, oil is understood to form from organic matter buried under high pressure and temperature over millions of years, with most original biological components believed to be destroyed in this process. However, this recent finding demonstrates that environmental DNA (eDNA) fragments have been trapped and preserved in oil deposits.
The study categorized different types of DNA found in the oil into three groups, allowing researchers to investigate species that inhabited Earth during various epochs, including ancestral marine organisms, primitive birds, and even traces of ancient hominids.
One of the most intriguing discoveries was the identification of DNA from marine species, suggesting that certain regions that are now land were once submerged underwater. This analysis supports the hypothesis of marine incursions during the Paleocene, approximately 37.5 million years ago.
Additionally, sequences of DNA matching those of ancestral birds were detected, indicating a possible molecular link between dinosaurs and modern birds. Fragments related to geographically distant species, such as yaks, turkeys, and kiwis, were also found, suggesting their ancestors shared habitats before continental fragmentation.
Notably, the study identified ancient human DNA fragments that do not correspond with modern populations. Some sequences show similarities to Homo erectus, an extinct hominin species that inhabited Asia around 500,000 years ago.
The oil samples analyzed were sourced from the Nanyang oil field in the Biyang Depression, China. This area has previously been studied geologically and revealed fossils of Homo erectus, indicating that this hominin once lived in the region. The preservation of these fragments in oil raises questions about their origin, with speculation that they may have originated from human remains trapped in geological layers that later generated oil.
This finding suggests that extinct hominin DNA could be more prevalent in the geological record than previously thought, opening new avenues for studying human evolution beyond traditional fossil analysis.
While oil is not considered a conducive environment for DNA preservation due to high temperatures and lack of water, the study suggests that certain mechanisms may have protected the genetic material over time. Remarkably, the recovered DNA shows no signs of deamination, a process commonly used to assess the authenticity of ancient DNA, indicating that conditions within the oil may have allowed for a distinct preservation compared to other fossil materials.
This research has significant implications across various scientific disciplines. In paleontology, the ability to recover DNA from extinct species through oil could complement the fossil record and enable molecular-level evolutionary studies. In geology, analyzing these DNA fragments could assist in reconstructing climatic and geographical changes over time.
Lastly, the identification of DNA in oil could have applications in industry, as genetic biomarkers may provide new insights into the formation and migration of hydrocarbons, enhancing exploration efforts.