1.First In Time is the theory that the first person who discovers property has possession and rightful ownership, and therefore the ability to convey title.
2.Cultivation and Improvement is an alternative to First in Time.  Under this theory, the interest of the party that is first in time can be trumped by a subsequent party that cultivates and improves the land
  a.Example – (Occupancy Theory) The English took the land from the Indians, and the US from the English on the theory that the Indians did not use the land to its highest and best use and therefore only had possession but not ownership