Men and women
should have such perianal skin folds radiating from their browneyes*. Friction and abrasion, from e.g. repeated and/or rough anal sex, usually wear them away or destroy their relative symmetry. The forensic medical field does consider the absence or abnormality of the folds significant in cases of anal rape (usually pediatric).
Personally, I think many more men than women have such folds these days. Hypocritical idiots who love to stick their penises into women's buttholes won't accept strap-ons and other objects up their own.
* As explained, with medical sources, in my sig's anatomy.html. Since people are so paranoid, here are some links from it with quotes:
"The anus is a longitudinal slit-like aperture which becomes oval during defecation... The skin surrounding the anal orifice is arrayed in radiating folds, the result of contraction of the corrugator cutis ani muscle."
http://www.intestinaldisorders.net/anatomy-anus-and-rectum.html"Peri-Anal Folds: Redundant perianal skin radiating from the anus... Peri-Anal Skin Tags: Extra skin that interrupts the symmetry of the perianal folds and does not smooth out with traction."
http://oja.state.wi.us/docview.asp?docid=13353&locid=97 (PDF; Medical-Forensic Terminology)
"Some fibers from this muscle become the corrugator cutis ani and insert on the perianal skin creating rugal folds and a puckered appearance."
http://www.health.am/ab/more/anorectal-diseases-general-anatomic-considerations/(There are also medical book refs that can be looked up with books.google.com, but this forum always fucks those links up.)