I'm sorry for misunderstanding the thing with the lions. Thank you for helping me understand it, it makes much more sense now.

As I said, living in groups is desirable to humans on a very basic level. It's what makes us survive and allows us to pass along our genes which is why staying in groups gives humans an evolutionary advantage.

I also said that what I described is how it used to work most of the time until the Neolithic Revolution happened. This enormous change also changed the way humans interact and behave. Stuff like greed and jealousy became much more common.

Despite that it is still baked into human biology that kindness and gratitude are advantageous to us. It explains the positive emotions that emerge when being kind and grateful.

I am also not doubting what you're saying about sociology because how could I? It's not wrong.

I think that our opinions don't differ that greatly. The only point I am making is that behaving in a social manner is indeed evolutionary advantageous because it undeniably is.

species that form groups through social interaction will result in a group of individuals that gain an evolutionary advantage, such as increased protection against predators, access to potential mates, increased foraging efficiency and the access to social information.

Is what Wikipedia says about group living.

You're assuming that you would be motivated to "return the favor," but where does that motivation come from?

It would come from gratitude. Being grateful is simply a tool that emerged to motivate animals, including humans, to live in groups. The behaviour I mentioned earlier can also be seen in chimps and other primates, whose behavioral patterns are pretty similar to ours.

TL;DR

Living in groups does have evolutionary advantages thus staying part of one's group is desirable which makes social behavior necessary. However, the Neolithic Revolution messed with human behavior and today's society being much larger than human groups used to be thousands of years ago complicates things further. Gratefulness is simply a tool that emerged in many species, including humans, to further the goal of staying part of the group. It is still baked into human biology although not as much as it used to be.