If that altruism came from a need to survive, then human nature isn't greed and selfishness.
There IS no one "human nature." Humans are and can be altruistic or selfish depending on circumstance, individual desire, socialization, whatever. (Not to mention the fluid definition of what's important to a person...the immediate family, the clan, the nation, whatever...) There's simply not any way to ensure everyone for all time adheres to a uniform "altruism." People do tend to act in self-interest; whether this self-interest results in altruism or competition is a contextual toss-up.