The following factor allowed Europeans or Eurasians to develop immunity to deadly diseases like smallpox measle and influenza:
- Europeans and Eurasians were able to develop immunity to deadly diseases like smallpox, measles, and influenza due to a process called natural selection. When humans started living in larger groups and settled in urban areas, they were more exposed to infectious diseases. These diseases spread rapidly, leading to high mortality rates. However, those who survived the infections passed on their genes to their offspring, providing some degree of immunity.
- Over time, populations with greater immunity to certain diseases had a higher chance of survival and reproduction, leading to the development of genetic resistance. In Europe and Eurasia, exposure to infectious diseases was higher than in other parts of the world due to urbanization, international trade, and colonial expansion. As a result, natural selection favored individuals with genes that provided immunity to these diseases.
- Historical evidence suggests that European populations had acquired immunity to some diseases before the discovery of America. For instance, smallpox was widespread in Europe during the Middle Ages, and many people developed immunity to it. When Europeans colonized the Americas, they inadvertently brought smallpox and other diseases with them, leading to devastating epidemics that wiped out a large percentage of the indigenous population.
Therefore, we can say Europeans and Eurasians developed immunity to deadly diseases through a combination of genetic resistance and exposure to infections.