Research in Evolution and Human Behavior has found an interesting relationship between a mother's gluteofemoral (i.e. butt and thigh) fat and her child's cognitive ability.

Essentially: hourglass-shaped women have smarter kids.

the fat gathered around the buttocks and thighs tends to hold deposits of omega-3 fatty acids (the human brain is comprised of about 8% omega 3 fats).

Waist-to-Hip ratio (WHR) is used to measure this affect: divide your waist measurement by your hip measurement. 0.6 to 0.7 is thought to be a good indicator of the hourglass figure.