After a thorough behaviorist undergrad education, I had to come to grips with determinism.
I decided that those types of altruistic behavior to the detriment of the organism demonstrate that all is not stim/response (SR) determinism.
Based on evidence CONTRARY to the 5 sense, the human ON FAITH sacrifices for the benefit of the other and not him/herself.
Some will say, "...but they did what they wanted..."
No, because they went contrary to what they preferred and what their 5 senses dictated.
They transcended SR determinism.
"Greater love has no man than this; that a man lay down his life for his friends...."