Fig. 4 |. Human and animal odour blends differ in the relative concentration of key compounds.

a, Odour profiles for humans, animals, and nectar-related stimuli. Named compounds made up >10% of at least one sample or an average of >1% across samples. Question marks indicate tentative identifications (see Methods). Animal samples were pooled by species prior to analysis (n=4 dogs, 2 guinea pigs, 1 sheep, 2 rats, 2 quail). Numbers beneath human samples indicate those used for imaging (Fig. 3g,h). b, Unscaled principal components analysis of host odour data from (a). c, Top ten loadings on first two principal components from (b). d, Proportion of human sebum made up of sapienic acid and squalene (data from ref⁵⁰). Oxidation of the two lipids produces volatile compounds enriched in human odour⁴¹.