Infectious diseases were the leading cause of death in the world before the introduction of antibiotics, and they have played a major role in the evolution of the human immune system.

Due to a lack of data, it has not been possible to accurately assess the effects of communicable diseases on human populations or to pinpoint the causes of many common ailments, particularly those that lead to child mortality.

Many of these diseases are caused by DNA-level chemically unstable viruses. There are no good records of ancient times and, as a result, it is often unclear why people got ill and died in the past.

While there is a good understanding of how the immune system of modern humans combats illnesses, but it is more difficult to figure out how the immune system of ancient humans functioned, Associate Professor of Ancient Biomolecules at the University of Tartu Christiana Lyn Scheib explained.

"Our past has shaped our immunity. To understand human immune system and account for inherited variations in illness prevention and treatment, it is crucial to understand their evolution. To do so, we must first understand how human immune responses have evolved over time and against which infections these alterations have occurred," Scheib said.

When a person is exposed to a pathogen, the body produces antibodies that remember the disease for the future. Antibodies remain in the bloodstream throughout a person's lifetime, retaining information about all pathogens to which they have been exposed. In the dying state, proteins and DNA from the bloodstream adhere to the teeth and can remain for millions of years.

"With all of this in mind, I developed a framework to conduct research that would provide me with an unprecedented overview of the history of diseases that have plagued people," Scheib said. She proposed to combine palaeoproteomics, ancient DNA and immunological research techniques in order to match ancient antibodies with relevant pathogens to identify ancient viruses such as measles, mumps and influenza from skeletal remains.

"As a result, we hope to learn whether disease exposure increased or decreased the chances of survival for long-lived humans, as well as how plague waves affected humanity," Scheib said.

On average, one in ten research projects submitted receives an ERC grant. Researchers from the University of Tartu have previously received a total of seven such grants. Director of the Institute of Genomics Professor Mait Metspalu praised the innovation of Christiana Lyn Scheib's project. "This project meets the ambitious standards for ERC funds. While, for example, we have studied the spread of medieval and earlier diseases by extracting the ancient DNA of pathogens from human remains, Christiana will examine the immune response of humans who have suffered from infectious diseases during their lives. If successful, this will provide a much more complete picture of the diseases prevalent in ancient populations," she said.

Metspalu added that the Institute of Genomics has a special laboratory for working with ancient biomolecules, whether they are DNA or proteins, which allows the study of hereditary biomolecules and antibodies from precious archaeological material in ultra-pure conditions, where the samples are well.

ERC grants are among the world's most prestigious and largest individual research grants.

There are a total of five categories of grants given, with scientific excellence serving as the primary evaluation criterion. The Starting Grant is given to early-stage researchers, and 408 outstanding researchers received €636 million total this year.

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