Ancient DNA Reveals 37,000-Year History of Human Disease
October 26, 2023
A groundbreaking study has mapped the DNA of 214 known human pathogens, stretching back an astonishing 37,000 years. Led by Professor Eske Willerslev, alongside Associate Professor Martin Sikora and Professor Astrid Iversen from the University of Oxford, the research offers unprecedented insight into the evolution of infectious diseases.
Researchers utilized specialized methods to analyze prehistoric disease DNA, creating a detailed catalog of pathogens throughout history. This isn’t just about the past; understanding these ancient diseases provides crucial context for those affecting us today, according to Professor Willerslev.
The study reveals a significant surge in zoonotic diseases – those transmitted from animals to humans – around 5,000 years ago. Professor Iversen explains this coincides with the rise of animal domestication and close proximity between humans and livestock.
“Keeping animals in large herds created ideal conditions for pathogens to spread amongst them,” Iversen stated. “This, in turn, dramatically increased the risk of transmission to humans through meat and milk consumption.”
Currently, approximately 70% of newly discovered infectious diseases are zoonotic, including well-known threats like salmonella, rabies, and MRSA. This highlights a critical link between lifestyle and disease exposure.
The findings underscore that the emergence of infectious diseases isn’t a fixed event,but rather a dynamic process heavily influenced by how we interact with the surroundings and other species. This research emphasizes the importance of understanding these past trends to prepare for future health challenges.
What role does enamel hypoplasia play in indicating past infectious diseases in ancient populations?
Ancient Teeth Reveal History of Infectious Diseases
Decoding Paleopathology in Dental Remains
For decades, archaeologists have understood that human skeletal remains can offer clues about past lifestyles, diets, and trauma. However,a growing field – paleopathology,specifically focusing on dental paleopathology – is revealing a far more intricate story: the history of infectious diseases as recorded within our ancient teeth. These tiny, durable structures act as time capsules, preserving evidence of pathogens that plagued our ancestors. Analyzing ancient dental remains allows researchers to trace the evolution and spread of diseases like tuberculosis, leprosy, and even early forms of influenza.
How Teeth Preserve Evidence of Past Illnesses
the unique structure of teeth makes them ideal archives of past infections.
Enamel Hypoplasia: Defects in enamel growth, known as enamel hypoplasia, frequently enough indicate periods of physiological stress during childhood, frequently caused by infectious diseases. These defects appear as visible lines or pits on the tooth surface.
Dental Caries & Periodontal Disease: While often linked to diet, the severity and patterns of tooth decay (dental caries) and gum disease (periodontal disease) can be exacerbated by systemic infections, weakening the immune system.
Bone Changes & Lesions: Infections like tuberculosis and leprosy directly affect bone tissue. Lesions caused by these diseases can be visible within the jawbone surrounding teeth, and sometimes even within the tooth itself.
Ancient DNA Analysis: Perhaps the most groundbreaking technique involves extracting ancient DNA (aDNA) from dental pulp – the soft tissue inside the tooth. This allows scientists to identify the specific pathogens present in an individual’s body at the time of their life. This is especially useful for identifying strains of bacteria and viruses.
Proteomic Analysis: Complementary to aDNA, proteomic analysis identifies ancient proteins left behind by pathogens, offering another layer of evidence.
Specific Diseases Revealed Through Ancient Teeth
Tuberculosis (TB)
Ancient DNA analysis of teeth has pushed back the known history of Mycobacterium tuberculosis, the bacterium causing TB, significantly.Studies have found evidence of TB in human remains dating back to 9,000 years ago in the near East, suggesting the disease emerged with the advent of agriculture and increased population density. Dental lesions consistent with TB have also been identified in skeletal remains from various archaeological sites globally.
Leprosy
Leprosy, caused by Mycobacterium leprae, leaves characteristic skeletal changes, particularly in the face and hands.However, aDNA extracted from teeth has provided crucial insights into the origins and spread of leprosy. Research indicates that leprosy likely originated in Asia and spread to Europe via trade routes. Analysis of ancient dental remains has also revealed different strains of M.leprae circulating in different regions, shedding light on the disease’s evolutionary history.
Influenza & Other Viral Infections
Identifying ancient viruses is challenging due to their fragile RNA genomes. However, advancements in aDNA techniques are making it possible. recent studies have successfully recovered fragments of influenza viruses from ancient dental pulp, providing clues about the origins and evolution of pandemic strains. Evidence of other viral infections, like those causing childhood diseases, can be inferred from enamel hypoplasia and other stress indicators.
Syphilis
the “Columbian exchange” hypothesis proposed that syphilis was brought to Europe from the Americas in the 15th century. However, analysis of ancient dental remains and skeletal material from before the Columbian Exchange has revealed evidence of treponemal diseases (the family of bacteria that includes syphilis) in Europe much earlier, challenging this theory and suggesting a more complex history of the disease.
Benefits of Studying Ancient Dental Pathologies
Understanding Disease Evolution: Tracing the genetic changes in pathogens over time helps us understand how they evolve resistance to treatments and adapt to new hosts.
Predicting Future Pandemics: By studying past outbreaks, we can identify factors that contribute to disease emergence and spread, potentially helping us prepare for and prevent future pandemics.
Improving Public health Strategies: Insights into the past impact of infectious diseases can inform public health policies and interventions.
Refining Archaeological Interpretations: Dental paleopathology provides a more nuanced understanding of past populations’ health and lifestyles.
Case study: The Medieval Cemetery of East Smithfield, london
The excavation of a medieval cemetery in East Smithfield, London, provided a wealth of skeletal remains, including numerous teeth. analysis of these teeth revealed high rates of TB and evidence of early strains of influenza. This data, combined with historical records, helped researchers understand the devastating impact of these diseases on medieval London’s population. The study also highlighted the unsanitary living conditions and overcrowding that likely contributed to the spread of infection.
Practical Tips for Researchers in Dental Paleopathology
Sterile Techniques: Maintaining strict sterile conditions during sample collection and analysis is crucial to avoid contamination with modern DNA.
Multi-Disciplinary Approach: Collaboration between archaeologists,microbiologists,geneticists,and dental professionals is essential for comprehensive analysis.
Advanced Imaging: Utilizing micro-CT scanning and other advanced imaging techniques can reveal subtle lesions and bone changes that might not be visible to the naked eye.
* Database Development: Creating comprehensive databases of ancient dental pathologies will facilitate comparative studies and accelerate research.
