Hello and thank you for the request.
Humans, as well as some animals, feel the need to be connected or belong for many reasons. One of the most important is to meet our basic needs for love, touch and connection. We can love ourselves, but without the attention from others like us, we would be unable to have the affirmation and comfort we need to know everything is ok with us and our world. When babies are born the touch of the parents or other caregivers allows that child to know they are safe and cared for. Without it, the child can die. So the act of touching and connecting is that basic to our survival as humans.
We also need to grow socially. We have various groups we belong to so we can meet our needs. Our family helps us connect in an intimate yet familiar way, our friends help us see ourselves from the world's point of view and our intimate relationships help us connect emotionally, sexually and physically. Without these ways to connect, we can suffer from depression, anxiety
or other psychological symptoms.
We also need to belong to a group that is larger than ourselves to help us define who we are. Being a citizen of the United States or being part of a yoga class, it is defining who we are. What groups we belong to by choice or not by choice can help us feel secure and more sure of ourselves. People often accept or reject the groups they belong to based on how belonging to that group fits who they feel they are as a person. And being part of a larger group can motivate us to improve ourselves. Without others, we may lose interest in ourselves and our world. Being part of a larger group also helps us intellectually. Other people's ideas, interacts and opinions help us think in a broader sense. It keeps us interested in our world.
Finally, if we are not socially connected, we are alone. And humans are not made to be alone. There are some individuals that prefer by nature to be alone for long periods of time (introverts), but eventually, we all need to connect in some way or another. To stay so isolated that we never have human interaction is seen as a way to punish or torture someone because our natures are to connect. We need to be with others.
I hope this has helped you,