Being social and selfess

Man is a social animal, they say.

What does it mean to be social? From the little I have learnt so far: It means being around other humans, humans whom you can communicate and co-exist with. Social humans get a sense of belonging around other humans. Sometimes, it means fitting in; other times, it means setting an example that leads other humans to a better life. But then, by this definition, all animals seem to be fit into the category of being social, don't they? Any animal that I can think of - dogs, cats, lions, elephants, tigers, monkeys, birds - seem to want to co-exist with other beings of their species. So, being social is not a unique trait to humans, its just how life has been throughout evolution.

Let's try another term. Being selfless. The opposite of selfish. A man is deemed as being selfish, when his actions seem to be benefit him, and him alone. Quoting http://en.wikipedia.org/wiki/Selfishness: Selfishness is placing concern with oneself or one's own interests above the well-being or interests of others.
Well then, selfessness is placing others concerns before your own. Why would a person do that? A person does any activity because there is a motivation. Motivation behind selflessness, then, would be the pleasure that the mind derives out of doing such an activity. So, isn't the mind then being selfish at this point? So, being selfless is being selfish, but with the difference being that your selfishness helps others rather than hurt them - is what I postulate. These terms are not true opposites. Selflessness is a kind of selfishness - the good kind.