Question

Please explain, from an evolutionary perspective, why diseases such as smallpox and measles had such a devastating impact on populations indigenous to the new world.

Answer 1

During the time period when smallpox and measles were prevalent and at their peak, human society wasn't introduced to the concept of vaccinization. This made these two viral diseases an endemic among populations. It owed to the evolutionary adaptations of these viruses which had undergone many mutations in becoming resistant to the human immune system and were able to survive the then popular antibiotics.

The concept of vaccines came later on when these viruses were injected into individuals in a weakened/killed state so that the individual can develop immunity against them without contracting the disease itself.