Ancient plague around Lake Baikal revealed by ancient DNA, and a prototype atom interferometer for dark matter

Overview

The podcast investigates how ancient plague affected early hunter gatherers around Lake Baikal, using skeletal remains and DNA to uncover plague infections thousands of years before medieval outbreaks. It also surveys exciting developments in other fields, including Iron Age bone tools, deep sea crustaceans, and a prototype atom interferometer designed to probe dark matter and gravitational waves.

Key insights

• Ancient plague infections were present among Baikal hunter gatherers around 5,500 years ago, with plague DNA detected in a significant fraction of individuals.
• Genomic data from both humans and pathogens illuminate burial relationships and possible transmission pathways, suggesting early zoonotic spillover from wild animal reservoirs.
• Marmot reservoirs and dietary exposure could have facilitated spread in the absence of flea transmission, potentially enabling large human-to-human transmission.
• A prototype atom interferometer using strontium clock transitions demonstrates a path toward measuring ultra-precise spacetime distortions, with implications for dark matter and gravitational wave science.

Introduction and framing

The podcast opens with an exploration of plague in ancient hunter gatherer communities near Lake Baikal, a region in Siberia known for a long history of human presence around the lake. Researchers have been examining burial grounds near the lake, including an especially informative site called Ust ida 1, to understand how plague affected people who lived there thousands of years before the well-known medieval outbreaks in Europe and Asia. The discussion emphasizes that the plague bacterium Yersinia pestis has multiple transmission modalities, and that ancient strains may have differed in their virulence and transmission potential from later medieval lineages.

Site and evidence from Baikal

The archaeologists describe four burial grounds around Lake Baikal, spanning centuries. A striking mortality pattern emerged at the oldest site, with a high concentration of adolescents and young people. The team extracted tiny amounts of DNA from tooth roots to recover both human genomes and pathogen DNA, achieving a 39% detection rate of plague across individuals, a remarkable figure given the time depth and preservation challenges. For comparison, medieval plague pits in London show higher detection rates, but that difference reflects context rather than a simple timeline, underscoring how extraordinary the Baikal data are for their period.

Genomics and social context

By sequencing the genomes of the humans interred at these sites, researchers could reconstruct kinship networks and relationships among buried individuals. Siblings were discovered buried together, parents with offspring, and in one case, two teenagers buried in the same grave appeared not to be closely related biologically, hinting at social or ritual connections that framed burial practices. The pathogen genetics were also revealing; alongside Yersinia pestis, related bacteria such as Yersinia pseudotuberculosis were examined to understand gene presence or absence and how these genes might influence virulence and transmission in ancient strains.

Key genomic findings and transmission implications

A major finding is the presence of a gene variant called ypm, associated with a pseudotuberculosis lineage, in the ancient plague strains. This gene could drive immune system overstimulation, potentially contributing to severe symptoms and high mortality, especially in young individuals with developing immune systems. The Baikal strains likely lacked the Yersinia pestis gene enabling flea-borne transmission (YMT prior to about 3,500 years ago), leading researchers to propose non-flea transmission routes such as pneumonic spread, which can be highly efficient between people. The work highlights that zoonotic spillovers from wild reservoirs, particularly marmots around Baikal, were a recurring feature and that such spillovers may have occurred multiple times in the region’s history.

Reservoirs and pathways

The marmot, a known plague reservoir in Central Asia, is thought to have interacted closely with Baikal hunter gatherers. The possible transmission routes include direct contact with infected marmots or undercooked marmot meat, which could facilitate human infection in the absence of fleas. These scenarios, combined with kinship networks and burial patterns, help explain how plague may have moved through communities long before agricultural settlements intensified in Europe.

Outlook and remaining questions

The researchers stress that while this Baikal data are compelling, there remains a broad missing record across Neolithic Eurasia. Additional data from Neolithic populations would help establish how widespread these early zoonotic outbreaks were and determine how the disease persisted or spilled over across different ecological contexts. The findings also contribute to broader debates about the lethality of early plague and the evolution of plague genomes, including how gene presence and loss shaped pathogenicity through time.

Other stories in the episode

In the podcast highlights, a separate Iron Age Scotland burial shows a woman with brain-removal marks and sharpened limb bones that may have served as tools, a study on giant deep sea crustaceans that possess extra copies of an ancient gene, and a feature on a prototype atom interferometer that could detect subtle spacetime ripples caused by gravitational waves or ultra-light dark matter. The atom interferometer uses clock transitions in strontium atoms to compare two spatially separated interferometers and shows how sharing a single readout laser can cancel laser phase noise, enabling future large-scale instruments. The interviewee describes a roadmap toward kilometer-scale detectors that could operate in concert with other observatories and potentially transform multi-messenger astronomy.

For more details, the Show Notes provide links to the original paper and related resources. Sponsorship messages from the episode are omitted in this summary as part of the content guidelines.