About a week or two ago, I started stretching with more purpose, a goal eventually being the full, flat pike, front and side splits, and a closed straddle. After getting quite close to a flat pike (that was a stretch I was doing beforehand), I noticed that my progress had halted almost completely in the side straddle, as well as a huge amount of pain in my hips. It usually doesn't bother me until I try again, and when I sit down I can sometimes pop the joints as one would their knuckles.
A friend described the reason being that "men's hips simply can't bend that way", which I would believe, had I not seen so many men performing splits. Is this something that needed to be done since childhood, or do I still have a hope of achieving my goals?