"Cities and other large settlements appeared for the first time during the Neolithic. Pathogens require a large host to thrive and these large, crowded populations provided a human host population that had not previously existed among hunter-gather societies (Armelagos et al. 1991:15). Now able to spread easily from person to person in the crowded conditions of cities, pathogens were able to exploit entire groups and reach endemic levels (Armelagos et al. 1991; Papathanasiou 2005). Crowded conditions paired with human settlements in close proximity to animals also contributed to high rates of infectious disease. In many early agricultural communities, animals were kept both near to and inside of houses. This proximity allowed some zoonotic diseases to transfer from animals to humans (Armelagos et al. 1991; Eshed et al. 2010). Contaminated water sources and close contact with human waste also facilitated parasitic infection in both animals and humans (Armelagos et al. 1991; Larsen 2006; Papathanasiou 2005). The increase of infectious disease associated with the adoption of an agricultural lifestyle did not necessarily increase mortality (Eshed et al. 2010). Those most likely to suffer fatal infections would have been infants, young children, and the elderly. Individuals who reached reproductive age had likely developed a resistance to such diseases (Armelagos et al. 1991)."