Sex is normally thought to function as a mechanism that injects heritable genetic variation into populations. But genetic mixing does not occur with self-fertilizers, and self-fertilizers have probably persisted since early eukaryotic evolution. I discuss the purpose of sex without genetic mixing and proffer that sex is a conservative mechanism that decreases heritable genetic variation. Syngamy (nuclear/pronuclear fusion/association + "mixing" of chromosomes) is a lesser-understood and lesser-studied aspect of sex. I propose that syngamy is a type of cell division that evolved from meiosis. In most metazoans, diploidy is restored via a cell division rather than through fusion event. I propose that meiosis and syngamy are pleiotropically controlled, and that they hypothetically share at least two homologous features that neither share with mitosis: (1) the requirement for membrane fusion/association, and (2) some products of the division are ontogenetically discarded.