Scientists have found DNA of salmonella and streptococci in archaeological sites from the Bronze Age.

The search for the sources of deadly infectious agents is extending further back into ancient archaeological periods. Recent discoveries indicate that humans encountered epidemics during the transition from hunting and gathering to agriculture and animal domestication. This suggests that many diseases originated from the wild. However, identifying traces of pathogens is challenging due to the nature of burials and the poor preservation of remains. To address this issue, an international team of researchers analyzed hundreds of samples spanning a timeframe of six thousand years.

2025-02-18 10:01:35https://naked-science.ru/article/archeology/uchenye-obnaruzhili-dnk

Humanity first encountered most zoonotic diseases, which have been transmitted to us from animals, around 10,000 years ago during the Neolithic Revolution. This was facilitated by close interactions with domesticated livestock, the processing and consumption of meat products, population growth, and crowding.

Researchers are striving to trace the origins of these infections—natural reservoirs and intermediary organisms. So far, discoveries have been infrequent. For instance, the causative agent of brucellosis was found in the remains of an 8,000-year-old sheep, and recently, media reported the discovery of DNA from the plague bacterium in a sheep from a Bronze Age settlement in the Southern Urals.

Scientists from several EU countries, Russia, and the USA decided to conduct a large-scale screening of samples from archaeological sites to see if they could find evidence of zoonotic pathogens. They analyzed 346 samples taken from 329 animal skeletal remains across 34 archaeological sites in Europe and Central Asia. The oldest site is Monjukli Depe, dating back 4,650-4,350 years BC, while the youngest is Giec in Poland, dated to the Middle Ages, around 900-1200 AD. Most of the sites date back to the Bronze Age, as previous studies have shown that ancestral forms of human pathogens are increasingly found in burials from this period. The results of this scientific work are published on the electronic archive of scientific articles and preprints in biology, bioRxiv.org.

All bones were classified by animal types, including wild representatives. Among them were horses, cattle, pigs, and goats. Some samples, most often from sheep, showed signs of diseases. DNA was extracted from the collected samples, sequenced, and analyzed against pathogen libraries. As a result, scientists identified 55 reliable signals indicating the presence of bacterial DNA.

The most dangerous bacteria found include Salmonella enterica, Bordetella petrii, Coxiella burnetii, Erysipelothrix rhusiopathiae. The oldest lineage of S. enterica extracted from human remains dates back 6,000 years. Researchers have now determined that its reservoir or carrier may have been sheep, goats, and dogs.

The bacterium E. rhusiopathiae is found in both vertebrates and invertebrates. It was recently identified in the remains of a medieval human in southwest England. This pathogen causes swine erysipelas, but it was also detected in cattle.

The majority of the microbes discovered are residents of the oral cavity and intestines of animals, particularly enterococci, staphylococci, and streptococci. They usually do not cause diseases, but they can pose a threat to individuals with compromised immune systems.

The authors of the study demonstrated that samples taken from pathologically affected areas of bones are particularly effective for identifying pathogens. This paves the way for further searches for the sources of ancient epidemics.