Cities played a large role in the evolution of the human immune system, researchers say on the National Geographic website.
In ancient cities, as today, people were more likely to get infections. Thanks to the fact that the human immune system has been able to train intensively during millennia of urban life, people are more resistant to microbes in areas with a long urban tradition, according to the latest research.
As biologist Mark Thomas of University College London explains, as cities grow, so does the number of microbes, and therefore people’s exposure to new diseases. Cities thus become a natural place for the evolution of human resilience.
People who survive the infection have a better chance of producing offspring that are resistant to it by passing on genes that make it resistant. The researchers therefore assumed that human populations, where urban life has existed for thousands of years, should have better disease resistance.
Thomas, along with Ian Barnes from the same university, decided to test their hypothesis. For this purpose, they conducted genetic research in several regions of the world, collecting DNA samples from 17 groups of people from Europe, Asia and Africa, including from Anatolian Turks, Sudanese or representatives of the Sami people in the north of Scandinavia.
Genetic samples were analyzed for resistance to tuberculosis, possibly associated with resistance to leprosy, leishmaniasis and Kawasaki disease.
It turned out that in Anatolia, where urban settlement has a tradition of about eight thousand. years, a high frequency of genes associated with resistance to tuberculosis was found. This frequency has not been found in the Sami people, nor in the Malawi people of Africa, where urbanization has a very short history, sometimes less than a century.
We were surprised how much the statistics confirmed our hypothesis, stresses Thomas. – Especially since when research is conducted in the field of evolutionary history, many factors may act due to the passage of time, which confuse the data.
The full results of the research were published in the Evolution journal (PAP).