Editing Pheromone (section)

=== Vaginal aliphatic acids ===
A class of aliphatic acids (volatile [[fatty acids]] as a kind of [[carboxylic acid]]) was found in female [[rhesus monkey]]s that produced six types in the vaginal fluids.<ref name= Michael>{{cite journal | vauthors = Michael RP, Bonsall RW, Kutner M | title = Volatile fatty acids, "copulins", in human vaginal secretions | journal = Psychoneuroendocrinology | volume = 1 | issue = 2 | pages = 153–163 | year = 1975 | pmid = 1234654 | doi = 10.1016/0306-4530(75)90007-4 | s2cid = 38274482 | title-link = copulin }}</ref> The combination of these acids is referred to as "copulins". One of the acids, acetic acid, was found in all of the sampled female's vaginal fluid.<ref name= Michael/> Even in humans, one-third of women have all six types of copulins, which increase in quantity before ovulation.<ref name= Michael/> Copulins are used to signal ovulation; however, as human ovulation is concealed it is thought that they may be used for reasons other than sexual communication.<ref name= Hays/>