Imagine uncovering a 5,500-year-old secret that could rewrite the history of a disease still affecting people today. That’s exactly what scientists have done, piecing together the genome of Treponema pallidum, the bacterium behind syphilis and other treponemal diseases, from ancient human remains found in Colombia. But here’s where it gets controversial: this discovery suggests these infections have been lurking in human populations far longer than anyone thought—possibly over 10,000 years. Published in Science, this breakthrough not only extends the known genetic history of the bacterium by 3,000 years but also raises questions about how these diseases evolved and spread across the Americas.
The remains, unearthed from a rock shelter near modern-day Bogotá, date back roughly 5,500 years. By identifying this ancient genome, researchers have revealed a previously unknown lineage of T. pallidum that doesn’t match any modern disease-causing strains. Geneticist Lars Fehren-Schmitz of the University of California, Santa Cruz, emphasizes the power of paleogenomics in unraveling the evolution of species and their impact on human health, both past and present.
Treponemal Diseases: A Complex Family
Treponema pallidum isn’t just one bacterium—it’s a family of three closely related subspecies, each causing a different disease: syphilis, yaws, and bejel. A fourth disease, pinta, is caused by Treponema carateum or a subspecies of T. pallidum. Despite their genetic similarities, the origins of these diseases remain shrouded in mystery. While skeletal remains can hint at infections, ancient DNA often tells a more intricate story, leaving gaps in our understanding of disease evolution.
A Lost Lineage Unearthed
The ancient DNA discovered in Colombia belongs to T. pallidum but doesn’t align with any known modern strains. Anna-Sapfo Malaspinas of the University of Lausanne suggests it could be an ancient form of the pinta-causing pathogen, though this remains unproven. Genetic analysis reveals this strain diverged from other T. pallidum lineages around 13,700 years ago, while modern subspecies split much later, about 6,000 years ago. This timeline underscores the diversity of treponemal pathogens in ancient times.
And this is the part most people miss: While the study doesn’t settle the debate over where these diseases originated, it highlights their long evolutionary history in the Americas, thousands of years earlier than previously known. Elizabeth Nelson, a molecular anthropologist at SMU, notes that this discovery adds crucial context to the ongoing discussion.
A Genetic Puzzle With Modern Implications
Tracing the origins of treponemal diseases is no easy feat. These bacteria are genetically nearly identical yet cause vastly different symptoms and spread in unique ways. Davide Bozzi of the University of Lausanne points out that this discovery pushes back the association of T. pallidum with humans by thousands of years, possibly into the Late Pleistocene.
The find was serendipitous. Researchers initially sequenced the individual’s DNA to study ancient human populations, generating 1.5 billion genetic fragments. During routine screening, teams independently detected T. pallidum traces, prompting a collaborative investigation. Despite bacterial DNA making up only a tiny fraction of the data, the depth of sequencing allowed them to reconstruct the genome without specialized techniques.
Interestingly, the skeleton showed no visible signs of infection, yet the tibia (shin bone) preserved the pathogen’s DNA. This suggests that even bones without obvious disease markers can hold valuable genetic clues, opening new avenues for ancient DNA research.
Why Does Ancient Disease History Matter Today?
Understanding how infectious diseases evolved in the past could help us predict their future behavior. Before publishing, the team shared their findings with Colombian communities, acknowledging the discovery’s significance to the country’s medical and cultural history. Miguel Delgado of the Universidad Nacional de La Plata stresses the importance of ethical collaboration, ensuring local communities are involved in interpreting and sharing such sensitive discoveries.
A Global Effort
This research was a collaborative endeavor, led by scientists including Nasreen Broomandkhoshbacht, Kalina Kassadjikova, Jane Buikstra, Carlos Eduardo G. Amorim, Melissa Estrada Pratt, Gilbert Greub, Nicolas Rascovan, and David Šmajs. Their work not only sheds light on ancient diseases but also sets a standard for inclusive and responsible scientific discovery.
Food for Thought
Could this ancient strain of T. pallidum still exist today, lurking undetected? And what does this discovery mean for our understanding of disease evolution and global health? Share your thoughts in the comments—let’s spark a conversation about the mysteries of our past and their implications for the future.
