3) Animals that engage in long term mating typically act altruistically towards their mates, which we will briefly touch on later.
Now, animals that engage in reciprocal altruism have also developed methods of avoiding exploitation:
Vampire bats have fast metabolisms and are therefore prone to starvation if they do not feed regularly.
When a starving bat has had an unsuccessful hunt, he will head over to a bat with a belly full of blood and give them a nudge.
The well fed bat will then feed the starving bat by regurgitating some blood.
Now, the important part is that the feeder remembers the starving bat and vice versa.
If the feeder one day finds himself starving, he will head over to a bat that he has previously fed and give him a nudge; thereafter he will typically be fed.
You scratch my back and I'll scratch yours.
However, if the previously fed bat refuses to repay the favour then the other bat will refuse to feed him ever again.
This is what we would call a grudge and humans experience it all too well, ranging from becoming mildly disgruntled when somebody doesn't say thank you, to attempting to kill your mechanic for ripping you off.
The latter example involves violence, which we won't go into here; however, now that you have an understanding of the link between genetic relation and altruism I'm sure that you can see why violence can be a rather effective behavioural strategy in certain contexts.
>Why do we want to be appreciated for ourselves?
Well, humans are social animals that live in social hierarchies.
Therefore, like other primates we must navigate social groups by means of evaluating the social prestige and dominance of others and ourselves.
We feel the need to be appreciated by others for a number of reasons.
Kin altruism leads us to feel the need for validation from our family members, while social prestige leads us to require validation from others.