Saul Feinman's research while affiliated with University of Wyoming and other places

... However, findings on female perceptions of male beards are equivocal. Some studies suggest that women prefer beards (Dixson et al., 2013;Hatfield et al., 1986;Reed et al., 1990), whereas others indicate that women favor clean-shaven men (Dixson et al., 2012;Feinman et al., 1977;Muscarella et al., 1996;Wogalter et al., 1991). These mixed results indirectly suggest that beards are more beneficial for intrasexual, rather than intersexual competition: beards may signal men's dominance and aggression toward other men. ...

... Frost et al. (2017) also assumed that the current frequency of hair colors in the population, where the prevalence of red hair is low, had stabilized and there is now an equilibrium between the rare-color advantage and the impaired health of people with red hair (Flegr and Sýkorová, 2019). Male preference for red, the rarest hair color, was not supported in several studies (Lawson, 1971;Clayson and Maughan, 1976;Feinman and Gill, 1978;Clayson and Maughan, 1986;Clayson and Klassen, 1989;Swami and Barrett, 2011;Guéguen, 2012). It was, however, partly supported by Wortham et al. (2018) who showed that red hair was preferred over other hair colors more frequently than expected based on the prevalence of redheads in the studied population (men preferred red hair 6% of the time, while only 3% of the female population were redheads). ...