SINGLE EVOLUTIONARY EVENT. “Meiosis is one of the ‘major innovations’ of eukaryotic life that evolved before their subsequent radiation over one billion years ago. Extant eukaryotes share a set of genes specifically associated with meiosis, implying that meiosis evolved only once before their last common ancestor.” (Brilliant review).
http://biorxiv.org/content/biorxiv/early/2016/04/28/050831.full.pdf