--Introduction--
Gender is a common topic for ridicule nowadays with the constant mocking of third genders by people predominantly on the right wing. Using arguments like "Biology only recognises two genitalia thus there is only two genders" but this couldn't be further from the truth. I was born with a chromosomal defect called Klinefelters Syndrome, this causes me to have a extra sex chromosome in my DNA which classes me as Chromosomally intersex. Intersex comes from one of two main issues, Being born with two sets of genitalia or being born with an sex chromosome set that doesn't match ones own anatomical structure. Biology doesn't just recognise two genders they recognise many more than that, because the basis of figuring out your gender pre-birth is from the use of looking at the babies hormone usage, sex chromosomes as well as ultrasound to figure out your genitalia. When it comes to the Biology of Gender looking at the genitalia means very little when there is a lot more going on inside of the body.
--Biological Genders--
Of course there is male and female but there are many more than that, more that although occur are rare enough that don't have biological names or diagnosis' as such. Klinefelters is common enough that it does have a name but that is down to reasons that deserve a whole separate discussion, KS (Klinefelters Syndrome) is what biologists and doctors call a Trisomy which is a type of Polysomy where there are more than 2 sex chromosomes present in the set. What does this mean for the individual with KS? KS can lead to infertility as the extra X Chromosome cuts off or limits the amount of testosterone that the person can produce, Testosterone needing to be actively produced to create sperm, it also leads to a mass production of growth hormone leading to many with KS being much taller than their parents or much taller than they would have been if it weren't for the KS, it can also lead to typically more female characteristics such as wider hips, gynecomastia (man boobs), etc. People with KS also have higher chances of getting certain diseases and health complications like breast cancer, Osteoporosis and Autoimmune disorders.
Polysomy's don't stop at XXY (KS) but can go into XXXY, X, XYY, XXXXX, etc. All of which leading to multiple defects, and all of this i am talking about is just Biological Gender, physical, observable gender differences outside of the binary.
--Sociological Gender--
Sociological Gender is what is commonly spoke about in context of people calling themselves Agender, Bigender, Genderfluid, Genderqueer, etc. Gender in Sociology is held as being something people put on everyday, the gender norms they adhere to or don't adhere to. Sometimes the gender expression isn't permanent in the case of Genderfluid people who may wear masculine clothing one day and feminine the other day, or to use the example my sociology lecturer uses is in the case of Drag Kings and Queens, people who are their biological gender most days but choose to express the opposite gender to what they privately express as a performance. But this is not the case of every gender.
The Gender someone identifies as is something inherent to them, they see that as a personal label that expresses how they feel psychologically and Socially, For example Agender people do not see themselves as either Male or Female Sociologically, they don't feel masculine or feminine enough to see themselves as either one of them. Agender to some could be a protest gender to say that the gender binary is wrong and needs to be revised for those who from experience have or do not fit their cultures gender norms.
The different theories within Sociology have inherently different perspectives on Gender. Marxism is gender-blind and says that all genders are exploited in Capitalism and that Capitalism devised the two gender binary as a easier way to discredit the labour of women in some fields and men in other fields, so gender should be abolished under a marxist society in order to create better understanding and a better environment where people are not judged or treated differently based on something they cannot help nor did they choose.
Functionalists view the gender binary as being useful in creating a smooth running society where the guidelines of the modern/nuclear family are kept, Functionalists say that Gender roles are necessary to keep a stable job environment, and that if they were deemed unfair they wouldn't have been created in the first place.
Feminists view gender as a patriarchal invention to keep women in their place, they see that overtime gender roles have changed from the old model of keeping women in the home as homemakers to working women, but while women are working they are still kept subservient to men and this shows and the gender roles for men have not changed. Men are still viewed and expected to be stoic, strong and confident while women are seen and expected to be subservient, quiet and feminine, as well in the workplace women are expected to go into caring jobs like Nurse, Teacher, Nanny and secretaries while men are supposed to go into strong jobs like fireman, police, soldier and mechanics.
--Anthropological Gender--
Gender changes from culture to culture, era to era and person to person. Cultures all over the world have had the existence of third genders for millennia from the Native Americans to Oman, third genders have existed and been widely accepted by their culture and people.
The Xanith (Oman)
The Xanith (also spelled Khanith) are a Third gender in Oman, they are characterised as being feminine in appearance, having same-sex relationships and hoping for one day to "become a man" and give up their androgynous lifestyle for marriage to a woman and having children.
Two-spirited (Native American Tribes)
Two-Spirited people are a third and fourth gender recognised in Native American tribes. They are characterised as wearing both male and female clothing. They are recognised by Cree, Ojibwe, Navajo and Lakota tribes in America and Canada.
The Hijra (South Asia)
The Hijra are a officially recognised Third Gender in much of South Asia including India. Hijra is considered neither male nor female in countries such as India, Nepal and Pakistan. They usually live in Communities with other Hijra's often adopting young boys who have fled their home from fear of being disowned for their sexuality or Gender. Many Hijra's are sex workers and in their communities they are led by a Guru.
--Sources--
[1] - https://www.genderspectrum.org/quick-links/understanding-gender/
[2] - https://monthlyreview.org/2014/06/01/marx-on-gender-and-the-family-a-summary/
[3] - https://www.enotes.com/research-starters/structural-functionalist-theories-gender
[4] - https://www.ksa-uk.net/