i get the impression that you are setting the parameters of this to confirm what you already want to confirm.
you are expecting to have evidence of someone doing something for others with no regards to their own subjective mind in order to say people can act selflessly. of course, we will have some reason for doing it. generally, because we feel it is the right thing to do. why do we get pleasure from helping others in need? similarly, we could ask why certain birds find the smell of a decaying carcuses as sweet and welcoming. the answer probably lies in general behaviors that are genetically driven.
like I said earlier, thats just a semantical argument by redefining what we generally mean by selflessness.
the issue of how we operate as an organism (as an individual with a subjective mind) is not the issue because I think we are unanimous in that’s how we function.
so any form of selflessness is going to occur within those constraints. and a good example of that is reciprocal altruism. their are plenty of people who do things that cost them though benefit someone else.
Ive got an aunt who is nearly 50 and today she gave her husbands sick father a bath. Of course she could have gotten my uncle to do it, but she selflessly did it.
What did she gain from giving an 80-something year old man (who recently suffered a stroke) a bath? Nothing. He needed the bath and she selflessly gave him one even though someone else could have done it.
What do I gain by waiting to hold the door for the person behind me as I enter a building? Nothing. They could have opened the door themselves just as I did, but altruism apparently has a biological purpose in us!
What does my niece gain by allowing my daughter to hang on to her Barbie for a couple of weeks? Nothing. She just wanted to “share.” She did not ask for nor did she get anything in return.
Even the teaching of morality to our children takes on selflessness. One thing I have a problem with religion is that it reinforces some valid morals from the wrong perspective. You shouldnt do bad things because God will punish you; and you should do good things because God will reward you. The concept is dripping with egotism. Rather we should teach that being faithful to your spouse ought not be about a fear of God, but out of respect for your spouse; and doing volunteer work for shelters ought not be about pleasing God but genuinely helping out those in need. In other words, we should do the right thing not because of what we aim to gain, but because how it effects our relationships with others and the stable foundations of society that it helps build. I would be real skeptical on you believing that we do everything for selfish motives. Reflect on your life and see if you can come up with any memory, emotion, experience, dream or nightmare that was solely centered around yourself. I doubt you can do it because our entire lives are centered around the relationships we have with others. This is where selfless altruism comes in.
If you look around you, you will see plenty of examples where people act selflessly. Again, going back to Anarchism. Many have noted that Anarchism is as old as human existence - if not older - because it is what the famous Anarchist, Peter Kropotkin, noted about other species in his book on Evolution at the turn of 20th Century, Mutual Aid. Scientific fields and terms like the golden rule, sociobiology, social evolution, reciprocal altruism, mutual aid and Anarchism all have a central theme in common: genuine concern for others.