When humans began to move out of Africa, they carried some of their pathogens to new areas, where they switched over to native hosts while native pathogens took up residence in the newly arrived humans. Agriculture and urbanization subsequently exposed us to yet more pathogens.
当人类开始迁徙出非洲的时候，他们把一部分病菌携带到了新地区，在那里他们把病菌传给了当地人，而当地的病菌也在新来人群身上定居下来。农业和城市化使我们接触了更多的病菌。如果那时候就有医生的话，他们会把所有这些都称为EID’s。