Is there a more noble act than human sacrifice for the survival of others? Christian teaching tells us there is not. The Supreme Being appeared in flesh, and then sacrificed himself for the saving of all believers. This tells me that although Jesus said the first commandment is to "Love your God with all your heart and all your soul and all your strength, and the second is to "Love your neighber as your self," that the act of sacrificing your life so that others may live supercedes all other behaviors. No amount of charitable donation, no amount of goodwill towards others, no amount of responsible behavior or penitence can compare to the simple act of giving up your life that someone else may live.
Easter always remind me of 9/11. I always think about (and mourn) the firefighters who climbed up into the Towers to bring people down, and how although they did not know they were doomed, the accepted their own demise as a very real possibility, and climbed the stairs anyway. Self-sacrifice is one of the only things I can argue is truly a "human" trait, you do not find animals (outside of hive-collective groups where there is not technically an individual) were self-sacrifice is a wide-spread and noticeable trait. Parent animals will often viciously and self-destructively defend their young, but this is simple Darwinism; it is easily argued the parents are not protecting their young out of love, they are doing so out of love of their own DNA. Humans, and as far as I know humans alone, will sacrifice their life for a complete stranger.
So the philosophical question doesn't become "what separates humans from animals?" but instead becomes "what connects humans, and humans alone, to the Divine?" The answer, I believe, is self-sacrifice. The answer is Jesus.