RT Journal Article SR Electronic T1 Information content of cheek and lip colour in relation to the timing of ovulation in women JF bioRxiv FD Cold Spring Harbor Laboratory SP 859801 DO 10.1101/859801 A1 Lucie Rigaill YR 2019 UL http://biorxiv.org/content/early/2019/11/29/859801.abstract AB Various animal species have evolved a sexual communication system with female displaying and male discriminating information about the timing of ovulation through sexual signals. More research is now investigating the potential ovulatory signalling function of female red skin colour in human and non-human primates. However, to date it is still challenging to draft satisfying hypotheses of the evolution and function of female red skin colour, due to methodological discrepancies between human and non-human primate studies. The present study used a within-individual design and objective methods to analyse the relationship between fine-scale variation in cheek and lip colour (luminance and redness) and the estimated day of ovulation in 15 cycling women. Lip, but not cheek, colour, appeared to contain information about the timing of ovulation, with lips getting darker around the timing of ovulation. This study adds to the growing evidence that female red skin colour may play a role in sexual signalling in human and non-human primates but also underlines variation in trait forms and functions at the species-level.