Parasites or cohabitants: Cruel omnipresent usurpers or creative éminences Grises ?

This paper presents many types of interplays between parasites and the host,showing the history of parasites,the effects of parasites on the outcome of wars,invasions,migrations,and on the development of numerous regions of the globe,and the impact of parasitic diseases on the society and on the course of human evolution. it also emphasizes the pressing need to change the look at the parasitism phenomenon,proposing that the term cohabitant is more accurate than parasite,because every living being,from bacteria to mammals,is a consortium of living beings in the pangenome. even the term parasitology should be replaced by cohabitology because there is no parasite alone and host alone: both together compose a new adaptive system: the parasitized-host or the cohabitant-cohabited being. it also suggests switching the old paradigm based on attrition and destruction,to a new one founded on adaptation and living together. copyright 2011 marcos a. vannier-santos and henrique l. lenzi.