In one sentence, describe what the following article is about:

Human beings are an intrinsically social species. Much of our species' success is due to our highly developed ability to cooperate and interact with each other. From an evolutionary standpoint, it is not surprising that instances of interpersonal rejection and social exclusion are negative experiences for individuals. There are many reasons why people exclude or ostracize others, so it can help to ask yourself why you are being excluded. Being excluded is not your fault, but it helps to understand how others think in order to learn how to make more friends. There are 4 main groups of people who are ostracized: People who hinder the group's operation. From an evolutionary standpoint, groups accept people who add something to the group. Those who hinder the group's operation can become excluded. Sometimes people are excluded because they are difficult to deal with. Other times, people are excluded simply for being different, and people naturally fear what they don't understand. The group has to learn to see this difference positively. People who are a danger to the group. Societies ostracize people who are aggressive, threaten the group's core values, who are untrustworthy, etc., as a way to protect the group. People who do not offer specific benefits to the group. Sometimes, a group feels that it already has enough members, so adding more will not add anything new to benefit the group. This isn't personal; the group just isn't interested in growing its members. People they are jealous of. If you have qualities that others don't possess, like high intelligence, athletic ability, beauty, musical talent, self-confidence, or any other positive trait, your presence may remind them of what they are lacking. This can cause resentment. This is their issue, not yours. Being excluded socially has been linked to depression, anxiety, substance abuse, alienation, poor academic performance, suicide, and even mass killings. Social ostracism can also change brain function and lead to poor decision-making. A recent study shows that social exclusion can sometimes be positive. Social exclusion of independently minded people who are proud to be unique can validate their sense that they are not like everyone else. In these cases, social exclusion can help spur creativity for the independent thinker. Being part of a clique may not always be fun. Cliques can be very stifling and may try to control how their members look, think, dress, and behave. Not being part of a clique can help you to stay true to yourself and to develop true friendships that do not stifle your creativity or individuality.

Summary:
Learn why being a social outcast hurts. Learn why social exclusion happens. Know how social exclusion can be harmful. Know that social exclusion can also be beneficial.