Instinct vs. Morals

In chapter two, CS Lewis  goes on to expand the topic of the Law of morality or decent behaviour.  The innate sense in us that help guide our decisions about what is right and what is wrong.  Is this an instinct or is it something completely different?  A definitition of instinct pulled from The Free Dictionary is:
 1. An inborn pattern of behavior that is characteristic of a species and is often a response to specific environmental stimuli: the spawning instinct in salmon; altruistic instincts in social animals.
2. A powerful motivation or impulse.
3. An innate capability or aptitude: an instinct for tact and diplomacy.

Wikipedia stated that: Some sociologists argue that humans have no instincts, defining them as a "complex pattern of behavior present in every specimen of a particular species, that is innate, and that cannot be overridden." Said sociologists argue that drives such as sex and hunger cannot be considered instincts, as they can be overridden. This definitory argument is present in many introductory sociology and biology textbooks,[6] but is still hotly debated.


Make a list of instincts and let's do some comparisons:
-self preservation (the desire to stay alive)
-greed
-sleeping
-sex
-aggression
-fight or flight
-herding
-mothering

So how does moral law factor into instinctive behavior?  Is it in and of itself and instinct or is it some other key component in our human nature.  CS Lewis argues that moral law is another part of human behavior, in effect our conscience that helps guide and control our instincts appropriately.  He used the example of a person drowning and calling for help.  Self preservation instinct would keep us away and on "safe" ground, yet our herding instinct will produce the desire to assist and help the person.  Moral law will guide the impulses to what is correct and right in that situation at that point in time. 

So is moral law just a form of education or social convention that we have learned over time?  We do learn things from people that are around us and our culture does mold us.  But think about it.... when we compare one culture to another culture, we are measuring them against each other and one may or may not come up lesser or greater then the other.  Therefore, we are measuring them against a common standard in order to make that decision.