I don't understand (or I am scared to understand?;). Do you mean we all evolved towards altruism? then this is contradictory, if we evolved (over 1000s of years) towards altruism then one can not modify instantaneously his evolved behavior depending contingently on if one belongs to the high or the low class. Or do you mean that the altruism "gene"(or whatever) is expressed only when one is in lower class? and that Altruism behavior is only expressed when survival is necessary, and is not a standard/general human behavior.