those who do not identify their sexual orientation or preferences, but remain open
Not really bisexual but similar in meaning, in which it involves people who are open to sexual relations, and/or affections, based on personal feelings, situations, and not on gender.
Closer in meaning to 'pansexual' or 'omnisexual' in that it does not conform to society standards defining the roles of gender in relations, both emotional and sexual.
The basic difference between 'Anthrosexual' and 'pansexual' is that one subscribing to being pansexual is determining their sexuality, defining it, while being Anthrosexual, one has NO defined orientation or preference. They simply do as they feel.
[A hybrid word, from the Greek Word 'anthro' meaning human and the Latin root 'sex' thus creating the literal word, human sexual]
Ancient civilizations did not have 'sexual orientation' as today's modern society does. Instead it was more contained by the roles taken by the parties involved, so that a person who was more aggressive, more dominant would take on the masculine role, while the submissive party was more 'feminine'.
There was no blurring between gender or actual consideration of gender in the sexual acts. It was determined by the 'roles played' rather than today's method of determining who does what, and who is allowed to do what.
History (Legend): As Ancient Civilizations, such as Rome, believed sexuality was about the roles taken, it was generally thought that the submissive person was more feminine, so that when a man took a submissive role, when older in years, they were more inclined to be ridiculed or looked down upon.
Noteworthy: Emperor Nero is believed to have taken the submissive role with a freedmen Doryphorous, and in doing so, imitated a young girl having her first sexual encounter.
There is also evidence that many soldiers of the time were sexually abused or taken by their higher ranking officers.