The phylogenetic position of extant tarsiers within the order Primates has been debated for much of the 20th century, and tarsiers have alternately been classified with strepsirrhine primates in the suborder Prosimii, or as the sister group to the simians (Anthropoidea) in the infraorder Haplorrhini. Analysis of SINE insertions, a type of macromutation to the DNA, is argued to offer very persuasive evidence for the monophyly of Haplorrhini, where other lines of evidence, such as DNA sequence data, remain ambiguous. Thus, some systematists argue the debate is conclusively settled in favor of a monophyletic Haplorrhini. In common with simians, tarsiers have a mutation in the L-gulonolactone oxidase (GULO) gene, which confers the need for vitamin C in the diet. Since the strepsirrhines do not have this mutation and have retained the ability to make vitamin C, the genetic trait that confers the need for it in the diet would tend to place tarsiers with haplorrhines.