The previous article in this series drew attention to the possibilities offered by eyebrows in the field of automated computerised gender classification. But eyebrows are by no means the only choice available to classifiers. For a recent (2015) roundup of the options on offer, see the work of Yingxiao Wu, Yan Zhuang, Xi Long, and Feng Lin, ‘Human Gender Classification: A Review’ (in: IEEE Sensors Journal, epub 2015)
“The aim of gender classification is to recognize the gender of a person based on the characteristics differentiating between masculinity and femininity. It is considered as the one of the most important application [sic] using pattern recognition method in the area of artificial intelligence.”
And then go on to list the currently documented possibilities. [See diag. above] They include: body, eyebrow, handshape, fingernail, gait, gesture, hairstyle, footwear, voice, blogging style etc etc.