As the world struggles with a global pandemic, a study of tens of thousands of old skeletons has revealed how the human body grows to fight disease, and how the diseases also spread. become more lethal over time. His findings could teach experts more about how we can adapt to deal with diseases in the future.
The researchers behind the new study say it shows how germs germinate to reproduce and ensure they survive beyond as many people as possible – but that this behavior also then reduces the severity of the disease over time. Eventually, the harmful microorganisms or pathogens end up reaching a kind of fairy with the human body.
Leprosy, tuberculosis, and treponematoses (a group of diseases including syphilis) were the diseases studied in the research. They can all leave marks on bones and teeth that indicate infection, and thanks to the remains of humans and available medical records, as many as 200 generations can be traced back.
“Each of these three diseases shows a decline in frequency as a result of mutually beneficial mutations for the disease and humans,” says anthropologist Maciej Henneberg, of Flinders University in Australia.
“In the last 5,000 years, before the advent of modern medicine, skeletal signs of tuberculosis became less common, skeletal displays of leprosy in Europe declined after the end of the Middle Ages, while skeletal symptoms of treponematoses declined in North America, especially in the years last year before they reportedly invaded Europeans. “
The researchers looked at three previous studies of the three diseases, covering a total of 69,379 skeletons. Across the studies observed, the age of these skeletons varied from as far back as 7250 BCE up to the present day.
Not all of these skeletons were from people with tuberculosis, treponematoses, or leprosy, and not all skeletons from people with these diseases would have shown physical signs on the bones. While this means that the new study is not a rigorous epidemiological meta-analysis, it does mean that the sample size was large enough for the team to make a useful profit.
None of the three diseases kill the human hosts immediately, which helps the pathogens to survive and spread. But the statistically significant decline in the frequency of tuberculosis, treponematoses, or leprosy over time suggests that either people became more immune or more susceptible or that the disease did less damage.
“From an evolutionary perspective, it makes sense for a pathogen to do less harm to the host it is responsible for surviving so high levels of spread appear to be a temporary evolutionary attraction that reduces how time goes by when we look at leprosy, tuberculosis and syphilis, “says anthropologist Teghan Lucas, of Flinders University.
Although there are some tables for reference – such as the different ways in which the three studies described their findings, and the need to consider other factors that may influence the spread of disease in addition to those is covered here – it is an interesting insight into the progression of diseases over time.
The COVID-19 coronavirus has only been with us for a short time, but we have already seen the viruses move and adapt to ensure its survival and to reach more human hosts. Even when vaccines get the spread of the virus under control, experts need to keep a close eye on how it grows in the future.
The new research is part of the growing field of palaeopathology, the study of ancient human diseases through evidence such as skeletons, mummified remains, ancient documents and literature, and art.
“Palaeopathology is becoming increasingly popular as a subject that allows diseases that appear on hard tissues to be studied in numbers in the past because the diseases are preserved for so long.” and there are the skeletons, “said Lucas.
“As a result of preserving signs of pathology on a skeleton, it is possible to trace the coagulation process of the three major infectious diseases as far back as finding samples.”
The research was published in PLOS One.