Researchers Uncover Ancient DNA from 12,000-Year-Old Fossils

In a groundbreaking study, researchers have successfully sequenced DNA from fossils dating back approximately 12,000 years. This significant discovery revolves around the remains of Torontoceros hypogaeus, an extinct species of ungulate uncovered during a subway construction project in Toronto in 1976. Until recently, the evolutionary relationship of this ancient creature remained elusive. Recent advances in DNA sequencing have revealed that Torontoceros is closely related to modern white-tailed deer.

The original excavation yielded a partial cranium and fragments of antlers, which were determined to be among the only known specimens of this species. The analysis conducted by a team led by Aaron Shafer, an associate professor at Trent University, highlights the potential of ancient DNA research in unraveling the mysteries of evolutionary biology.

Extracting DNA from Ancient Remains

The process of extracting DNA from ancient bones is meticulous and demands a sterile environment to prevent contamination. As Aaron Shafer explained, researchers must operate in labs equipped with ultraviolet lights to eliminate any external DNA. Wearing sterile “bunny suits” and N95 masks, scientists take further precautions by blasting the fossils with UV light and scraping away the outer layers before drilling into the bone to collect fine powder.

This powder, containing potential DNA fragments, is crucial for analysis. Researchers hope to find cells within this material that can yield usable genetic information. The extraction process is fraught with challenges, as the presence of modern DNA from the environment can complicate results.

The Dual Nature of DNA Sources

Interestingly, while external DNA contamination poses a challenge in some cases, it can also be an asset in other research. For instance, Nicolas Rascovan from the Pasteur Institute studied teeth from soldiers who perished during Napoleon’s retreat from Russia in 1812. His team focused on identifying the pathogens responsible for their deaths, revealing that enteric and relapsing fever were significant contributors.

The isolation of DNA involves sophisticated techniques. Rascovan’s team dissolved non-DNA materials from the tooth samples using chemical reagents. The remaining solution was mixed with silicon powder, allowing the negatively charged DNA strands to bond with the positively charged silicon, enabling further analysis.

Digitizing and Analyzing Ancient DNA

Following extraction, the DNA must be digitized for analysis. Various sequencing machines are employed, with Illumina machines being among the most prevalent. These devices utilize a library of synthetic DNA molecules, known as adapters, to tag and identify the DNA strands for sequencing. The sequencer captures images of the samples, decoding the nucleotide pairs and converting them into digital data.

Despite the technological advancements, working with ancient DNA presents unique challenges. DNA from older samples often suffers degradation, making it crucial for researchers to employ chemical methods to restore missing sequences. Shafer noted that comparing ancient DNA to fresh samples can reveal deviations that indicate damage, guiding the restoration process.

Both Shafer and Rascovan acknowledge the role of luck in their research. Factors such as time and environmental conditions can significantly affect DNA preservation. However, advancements in technology have enhanced the ability to analyze increasingly older samples. Shafer pointed to a recent study that successfully identified DNA from fossils over 1 million years old, underscoring the potential for future discoveries in ancient DNA research.

The exploration of ancient DNA not only sheds light on the evolutionary history of species like Torontoceros but also provides insights into historical events, such as the conditions faced by soldiers during wartime. As researchers continue to refine their techniques, the possibilities for uncovering the past through genetic analysis grow ever more promising.