SOCIAL REGULATION OF DEATH. “”The emergence of a genetic program allowing a social form of regulation of cell survival and cell death, through a process of ‘altruistic’ cell suicide, has been considered as one of the solutions that evolution has provided to the specific problem of multicellular bodies and attributed to the selective pressure that applied to the emergence of multicellularity, including a process of kin selection between cells sharing the same genome and condemned to live together.”
http://www.nature.com/cdd/journal/v9/n4/full/4400950a.html