It seems that thus train is going to a world where humans are an entirely sexless race. They have males and females of course, if you want genderless that's a few tracks down. This train is going to a world where humans just never evolved the capacity to see sex as something pleasurable.
Humans in this world don't get horny at all, don't experience sexual attraction, and can't feel any erotic sensations, and don't orgasm at all. Genitals are built differently, penises lack heads or foreskin, and get hard and shoot seaman at will, while vaginas don't have clits or any folds outside the outer crack, just being little holes to deposit seamen in quickly, and neither are feeling any pleasure.
Of course, this world had advantages, there are no taboos about who you can touch, or about physically affection, nor are there any taboos about being visibly nude. It's quite a fun place to go if you like your partners oblivious and don't mind giving up some sensations.
Now let's see who on the train we'll follow