Red blooded, and even more Maroon blooded humanoids tend to have specialized bloodlines. We all know that sorcerers are the best at honing in their skills at casting. But many red blooded creatures have at least a trace of a bloodline that gains them bonuses regardless of class.
These Bloodlines work as a pathfinder trait, but as you level up you can unlock extra bonuses. These bonuses can range from gainning a class skill, skill bonuses, to as much as bonus spells and even extra senses. A person can only have one bloodline, and some bloodlines are locked to only certain species.