ESCAPING EXTERNAL CONTROL. “Interestingly, the finding that a cell suicide program is operational in several unicellular eukaryote lineages explored to date support the seemingly paradoxical view that genetic mutations that would allow cells to escape environmental regulation of their suicide machinery may have become counterselected at the level of the colonies of these single-celled eukaryotes.”
http://www.nature.com/cdd/journal/v9/n4/full/4400950a.html