“The concept of there being only two sexes, male and female, is a social convention and is not a biological reality or a scientific reality.”
You must not have been in the same locker rooms I’ve been in. Or owned the same dogs and horses I’ve owned. With rare exceptions due to genetic problems, there are two sexes. One would be amazed at how few male animals will accept getting a penis stuck up their rumps, or how many female animals substitute being licked by another female.
If you want to argue a social convention asserting there are but two typical sexes among humans, then by all means do so with an honest acknowledgement of the biological reality in which “biological sex” encompasses far more than just two types of sex. Just don’t lie to yourself and to other people falsely claiming there are only two biological sexes. There are not just two biological sexes and there never have been.
It appears from your comment that you failed to learn elementary sex facts from your ownership of those dogs and horses. In our own experience with producing cattle, hogs, horses, mules, dogs, cats, chickens, turkey, Guinea, Peacock, fancy pigeons, corn, sorghum, wheat, rye, barley, soybeans, cotton, tobacco, peaches, pears, cherries, blackberries, tomatoes, potatoes, sweet potatoes, Swiss chard, spinach, pole beans, lettuce, radish, cucumber, zuchinni, squash, watermelon, cantaloupe, honeydew, Crenshaw melon, oranges, lemons, grapefruit, avocado, plums, thyme, oregano, marjoram, mint, onions, chives, garlic, dozens of hybrid and species flowers, and our own cross-breed Bearded Iris and Beardless Iris, we have observed a variety of variations in the sexes and sexual behavior of those organisms. If a person had to judge from your comments, it appears you are willfully remaining ignorant in defiance of reality. You are simply acting out in boorish ignorance and stupidity.
Kitties lick each other all the time.