9.14-What is the reason that humans like to group together in interest groups?

9.14-

There is something very powerful about working out the body with others.  The military has shown that during boot camp and beyond troops grow as a "band of brothers".  This bonding comes through going through hard times together.  Crossfit and Gladiators and other programs have used this to be a part of the benefits of the workout experience.  We were not meant to live isolated lives.  We were created to enjoy life in groups.

Ecclesiastes
4.
Two are better than one,
    because they have a good return for their labor:
¹⁰ If either of them falls down,
    one can help the other up.
But pity anyone who falls
    and has no one to help them up.

Mark 1.
¹⁶ As Jesus walked beside the Sea of Galilee, he saw Simon and his brother Andrew casting a net into the lake, for they were fishermen. ¹⁷ “Come, follow me,” Jesus said, “and I will send you out to fish for people.” ¹⁸ At once they left their nets and followed him.
¹⁹ When he had gone a little farther, he saw James son of Zebedee and his brother John in a boat, preparing their nets. ²⁰ Without delay he called them, and they left their father Zebedee in the boat with the hired men and followed him.

Mark 2.
¹³ Once again Jesus went out beside the lake. A large crowd came to him, and he began to teach them. ¹⁴ As he walked along, he saw Levi son of Alphaeus sitting at the tax collector’s booth. “Follow me,” Jesus told him, and Levi got up and followed him.
¹⁵ While Jesus was having dinner at Levi’s house, many tax collectors and sinners were eating with him and his disciples, for there were many who followed him. ¹⁶ When the teachers of the law who were Pharisees saw him eating with the sinners and tax collectors, they asked his disciples: “Why does he eat with tax collectors and sinners?”
¹⁷ On hearing this, Jesus said to them, “It is not the healthy who need a doctor, but the sick. I have not come to call the righteous, but sinners.”