How did the monastic tradition evolve? In the 4th Century there was a strong monastic tradition, which usually involved living in solitude or small groups in the wilderness. By the 12th Century the monastic life was being lived in large groups, and generally close to large communities. How did one tradition evolve into the other?
Monasticism was unknown until the end of the third century. Paul expressed that he preferred celibacy, but there was no "command from the Lord" to remain unmarried. (Simon) Peter, according to Catholic tradition the first Pope, was himself married.


  Luke 4:38 And he arose out of the synagogue, and entered into Simon's
  house. And Simon's wife's mother was taken with a great fever; and
  they besought him for her. 
  
  MATTHEW 8:14 And when Jesus was come into Peter's house, he saw his
  wife's mother laid, and sick of a fever.


Widows were treated with special respect, but encouraged to remarry and bear children if still within child bearing age. More emphasis was placed on missionary and charity work than meditation or spiritual development.

Over time, the custom developed of going into the desert (or otherwise being alone), when faced with an important life decision, a desire to commune with God, etc. These people were called hermits, a term which means "desert dwellers". The most famous of these early hermits was Anthony of Egypt (251-356). Athanasius' Life of St. Anthony began to make the hermit life popular, both because it portrayed it as a path to eternal life, and because Anthony was portrayed as an athlete for Christ, a heroic figure.

Now there were so many hermits that it was starting to get crowded. A hermit named Pachomius (290-346) instituted some rules; that the monks should live in isolated huts, produce their own food and clothing, and should never speak to one another. Because they were no longer dependent on public charity, their growth was unlimited, and monasteries and monks began to spread rapidly.