structural:expansion, linguistic:paraphrasing, quality:corruption
Origin of meiosis

Meiosis appears to be a fundamental characteristic of eukaryotic organisms and to have been present early in eukaryotic evolution. Eukaryotes that were once thought to lack meiotic sex have recently been shown to likely have, or once have had, this capability. As one example, Giardia intestinalis, a common intestinal parasite, was previously considered to have descended from a lineage that predated the emergence of meiosis and sex. However, G. intestinalis has now been found to possess a core set of meiotic genes, including five meiosis specific genes. Also evidence for meiotic recombination, indicative of sexual reproduction, was found in G. intestinalis. Another example of organisms previously thought to be asexual are parasitic protozoa of the genus Leishmania, which cause human disease. However, these organisms were shown to have a sexual cycle consistent with a meiotic process. Although amoeba were once generally regarded as asexual, evidence has been presented that most lineages are anciently sexual and that the majority of asexual groups probably arose recently and independently. Dacks and Rogers proposed, based on a phylogenetic analysis, that facultative sex was likely present in the common ancestor of eukaryotes.