In modern workout/cycling gear, and from the rear while cycling, most backsides look very similar anyway. The black stretchy pants do their job. I have to look at the rest of the body to determine gender. Look at the waist/hips, then move up. Females will usually have on a top with some kind of cutout in the back showing skin and sports bra. The ponytail used to be a giveaway, but not anymore. I personally think that the women are looking at and evaluating each other more than the men. The ladies have their outfits matching just so and work hard to do that. Men, on the other hand, any pair of shorts and a shirt will do. If they do not clash, all the better.