The gluteus maximus is the most superficial as well as largest of the three muscles and makes up most of the shape and form of the buttock and hip area.
It is large and powerful because it has the job of keeping the trunk of the body in an erect posture.
Big buttocks are a sheath of fats stored in the gluteal area layering the gluteal muscles.
Big buttocks in men are a result of too much oestrogen in the body due to what is known as AROMATIZATION which is the conversion of Testosterone to oestrogen.