Final answer:
The correct consequence of the transition to intensive agriculture is that it made it easier for contagious diseases to spread and reach epidemic levels, due to increased population density and permanent settlements.
Step-by-step explanation:
The transition to intensive agriculture during the Neolithic Revolution brought significant changes to human societies, including an increase in population density and a sedentary lifestyle. With the growth of densely populated settlements, contagious diseases found fertile ground to spread among humans. These conditions were particularly advantageous for diseases like malaria, which thrived due to the proximity of humans to mosquito breeding grounds. The large, stationary populations also experienced more epidemic diseases, closely tied to the substantial amounts of human and animal waste and the dependence on consistent weather for crops.
Unlike the scenario presented in option a), where diseases were reduced or eliminated, the settling down of human populations led to the opposite. While option b) suggests that parasitic diseases first appeared among humans with the advent of agriculture, in reality, they may have affected humans before but were exacerbated due to the new living conditions. Therefore, the correct answer is option c): The transition to intensive agriculture made it easier for contagious diseases to spread and reach epidemic levels due to increased population density and permanent settlements.