Kindness
For close relatives, there is a strong altruistic instinct because of shared genes. For others, reciprocal altruism has evolved.
Reciprocal altruism
In the prisoner’s dilemma game, every player has an option of being nice or nasty. For repeated games of the prisoner’s dilemma, in a famous tournament conducted by Axelrod, ‘tit for tat’ won. ‘Tit for tat’ says: ‘Be nice first. In round i do what the opponent did to you in round i-1.’ Observed in the period of truce between the British and the Germans in WW1 trenches. Also seen in vampire bats which vomit some blood for bats who did not get a meal, but who have not refused them in the past. But it is not perfect: there is the problem of endless retaliation when two quasi-tit-for-tat players play each other and one of them happens to be nasty initially. This problem is solved by randomness.
Smarter models would generalize past experiences and learn how to react to various kinds of situations.
Social reputation
Thus cultures of man have developed to praise kindness and heroism, especially if it is conspicuous. They have also developed means of spreading along reputation: awards are an example.