Explain why there were so many deadly diseases that the Eurasian brought over to the New world but with the exception of syphilis, not many deadly disease were brought to the Old world from the Americas?
The disparity in the transmission of deadly diseases between Eurasia and the Americas can be largely attributed to factors such as population density, domestication of animals, and historical isolation. Let's break it down:
1. Population Density: Eurasia, especially regions like China, India, and Europe, had higher population densities compared to the Americas. Dense populations created conditions for the rapid spread of infectious diseases, enabling pathogens to evolve and become more deadly. In contrast, the Native American population was significantly smaller and less concentrated, which limited the opportunities for diseases to spread and mutate.
2. Animal Domestication: Eurasians had a longer history of animal domestication, leading to close proximity and increased interaction with domesticated animals. This close association exposed them to a wide range of animal-borne diseases, some of which adapted to also infect humans. For instance, diseases like measles, smallpox, and influenza originated from domesticated animals such as cattle and pigs. Native Americans had limited domesticated animal species, which restricted the transmission of diseases.
3. Historical Isolation: The Americas were geographically isolated from the rest of the world until the late 15th century when Europeans arrived. This isolation resulted in a lack of exposure to certain pathogens present in Eurasia. When Europeans came to the Americas, they unintentionally introduced a plethora of infectious diseases, to which the Native Americans had no prior exposure or immunity.
4. Genetic Resistance: It is also believed that genetic differences between Eurasians and Native Americans played a role in the disparate impact of diseases. Over centuries, Eurasians developed genetic resistances to many infectious diseases, passed down through generations. Native Americans, having never been exposed to these diseases, lacked such genetic defenses, making them more susceptible to new infections.
In the case of syphilis, it is interesting to note that its origin is still a topic of debate, with some theories suggesting it may have existed in the Old World before Columbus, while others argue for a New World origin. Nevertheless, syphilis did spread to Europe and elsewhere following Columbus' journey, likely due to its ease of transmission.
In summary, the combination of higher population densities, animal domestication, historical isolation, and genetic protections contributed to the contrasting transmission of deadly diseases between Eurasia and the Americas.