Skinny girls are obviously not getting enough nutrition, which means their kids won't be as healthy.

Big booty and nen-nen girl are healthier, which means babies also healthier.

Also? Who say no evolutionary purpose? Girls with big booty and nen-nen are more likely to get wealthier husbands which means more and healthier babies too.

Those girls who say no evolutionary purpose just jelly they don't have big booty and nen-nen.