I hate to be a stickler but I believe the OP is looking for our "sex" rather than our "gender". Sex refers to either of the two major forms of individuals that occur in many species and that are distinguished respectively as female or male on the basis of their reproductive organs. Whereas, gender refers to the behavioral, cultural, or psychological traits typically associated with one sex.

Sure, you could ask everyone what their gender is, but many people don't even know their own gender. And those who do would probably never tell you anyway. There is just way too much discrimination surrounding gender today. And, another problem is that gender is not black and white. People can lean strongly one way or the other, or be right down the middle.

While most people are unwilling to share their pschological gender traits with the world, there are many physical traits that can't be so easily hidden. The two most noticeable are finger length, and hair spiral direction. Individuals possessing mostly female gender traits will generally have an index finger (on one, or both, hands) that is longer than their ring finger. Very feminine women, gay, and transgendered men will typically possess this trait, whereas, very macho men, and lesbian women, will generally have a shorter index finger than their ring finger. Hair spiral direction is another very visible clue, clockwise for male and counterclockwise for female.

If you don't think the gender lines are blurred, just walk into any honky-tonk on a Saturday night where you can see all the cowboys cleaned-up pretty and twirling about in their pointy heels and frilly shirts. Or, think about the huge numbers of women who are fans of professional sports that they are not even allowed to participate in. The world of male dominated sports is clearly an outlet for men's primitive need to do battle while living in a "civilized" world. Women are abused by their husbands and boyfriends ten times more on Super-bowl Sunday than any other day of the year! It's the single biggest domestic violence day of the year, yet many women love it.

Of course, if the OP really wants to know about our gender rather than our sex perhaps we should should just post pictures of our hands.