Final answer:
The original Georgian colonists' mortality within the first year was not significantly caused by 'Countless attacks by the Spanish and Natives', but rather by hard labor, poor sanitation, and climate changes. The Native Americans' lack of immunity to European diseases like smallpox severely affected their populations.
Step-by-step explanation:
The deaths of the original colonists within the first year in Georgia were caused by several factors, including hard physical labor, poor sanitation, and changes in climate. However, the option stating 'Countless attacks by the Spanish and Natives' did not significantly contribute to the mortality rates of the original Georgian colonists within their first year. While there might have been skirmishes and conflicts with Spanish forces and Native Americans later, it was not a leading cause of death among the early settlers of Georgia particularly within that initial timeframe.
Regarding Native Americans, the primary reason they were severely affected by smallpox was because they had no immunity to European diseases, such as smallpox. These microbes were introduced by Europeans and resulted in devastating epidemics among the indigenous populations. Factors such as malnutrition, due to disrupted food sources and lifestyle, exacerbated these communities' vulnerability to diseases.