A research study suggests that signal convergence between the sexes may reflect strong selective strain on family recognition through olfactory cues. Signal convergence through olfactory cues within the sexes actually arises as its by-product or it can work independently to prevent competition between unfamiliar relatives. There is a link between an individual's genome and their olfactory signals that could be mediated by pathways producing semiochemicals or even by carrier proteins modifying the individual bouquet of olfactory cues.
So, we are biologically designed to be able to smell out our relatives, but only our blood relatives. The thing is that we can’t smell out our spouse, because this is biological signal convergence. The biological ability could be a clue to humans of kin recognition to avoid inbreeding and nepotism. Other primates take part in nepotism and inbreeding, and these olfactory clues may help explain another way that we are separated from animals.