HIGH CERTAINTY. “During the course of this evolutionary trajectory, the last eukaryotic common ancestor became sexual, reassorting and recombining chromosomes in a process that entails regulated fusions of haploid gametes and diploid → haploid reductions via meiosis. That the last eukaryotic common ancestor was sexual is no longer a matter of speculation/debate as evidence of sex, and of genes exclusively involved in meiosis, has been found in all of the major eukaryotic radiations.”
http://cshperspectives.cshlp.org/content/6/3/a016154.full