Fairness comes in different varieties, which may work together:
proportionality (distribution according to work put in)
equality (equal distribution)
distribution according to need
Fairness and cooperation reinforce each other. Cooperation may be described as what
you put in to a situation; fairness refers to what you get out of it. If people
are treated fairly (whatever that means in the context) then they are more motivated
In modern “primitive” societies of hunter-gatherers, there is egalitarianism (a very
flat power structure with all members of the group contributing to decisions) and
distribution according to need, so that all members of the group are cared for.
Our nearest relatives, the comparatively unevolved chimpanzees and bonobos, do not
share like humans do; typically, high-ranking individuals dominate the proceedings
and eat first. It is thought that egalitarian sharing in the human way evolved because
we started scavenging and capturing large prey animals where there was a lot of meat
to go around and cooperation was necessary to secure a carcass or kill the prey.