Father nose best

Abstract

Olfaction is the main sensory modality for many animals, but the importance of smell to humans is not so clear. However, a number of researchers have demonstrated that the human sense of smell, similar to that of many animals, might form part of the individual recognition and mate choice processes, albeit at a subconscious level. The mechanism by which the distinct odour of an individual arises is due in part to the highly polymorphic human leukocyte antigen (HLA) loci. The HLA are the human equivalent of the major histocompatibility complex (MHC), which influence a number of olfactory-related behaviours in rodents, including nesting, pregnancy block, individual recognition and mate choice.It is generally thought that most animals, including humans, base much of their odour preference on their own odour and those odours to which they were exposed as infants. However, there is some evidence for a heritable component to odour preference, although a genetic effect is difficult to prove owing to the many environmental variables that not only influence the preference, but also the odour production. In addition, the high level of variation at the HLA loci in the general population also adds complications to a genetic analysis in humans. However, a recent study [1xPaternally inherited HLA alleles are associated with women's choice of male odor. Jacob, S et al. Nat. Genet. 2002; 30: 175–179Crossref | PubMed | Scopus (273)See all References][1] demonstrates that there is indeed a genetic influence on odour preference in humans and, by using members of an isolated community of German–Austrian descent, the researchers were able to investigate how this choice varied with a limited number of HLA alleles.Females were asked to report on the ‘familiarity’, ‘intensity’, ‘pleasantness’ and ‘spiciness’ of the odours from males from a wide-range of ethnic backgrounds. What was evident was that the women preferred the odours of those males whose HLA most closely matched their own (although they did not perceive these as familiar). However, in a subtle twist, the preference was not just for similar HLA to their own, but for odours that came from individuals with similar HLA alleles to those that the women had inherited from their fathers; that is, a paternal effect. Additionally, the authors show that this effect has a genetic basis, as the preference co-varies only with those HLA alleles the women inherited from their father, rather than all the HLA alleles their fathers possess.This indicates a genetic parent-of-origin effect (POE) on odour preference, a phenomenon that can most readily be explained by genomic imprinting. Interestingly a study using mice [2xUrinary odour preferences in mice. Isles, A.R et al. Nature. 2001; 409: 783–784Crossref | PubMedSee all References][2] produced results that are strikingly similar to those of Jacob et al. In this investigation both male and female mice were shown to prefer paternal odour cues and this preference was also subject to a genetic POE. Although it is difficult to determine a mode of action for these POEs, what is germane is that this phenomenon could be an underlying mechanism behind kin-biased behaviour, such as mate choice, communal nesting and social behaviour in species as diverse as mouse and man.