A study from the University of London has found that because people in urban areas "intermingle far more closely," city dwellers are more resistant to disease.
Researchers analyzed DNA samples from 17 populations across Europe, Asia, and Africa and found that people who hail from areas with a longer history of urbanization and were once disease-ridden cesspools rife with death and suffering were more likely to carry specific genes that give them resistance to tuberculosis and leprosy.
Scientists call it "selective pressure," a type of "survival of the fittest" phenomenon that occurs when populations are exposed to deadly illnesses and those who are best genetically equipped to resist disease pass the resistance along to their offspring.
Since cities have denser populations, the likelihood of disease infection increases, but so too does the spread of resistance genes. So rejoice, slutty urban dwellers! Keep intermingling closely and your selfless sacrifice will save our children from the clap.