How did the concept of paradise develop
The idea of paradise is today associated with the major monotheistic religions. However, the roots of this concept are more complex and developed from earthly ideas and religious structures.
In early Sumerian civilization, deriving from ancient Mesopotamia, the gods were seen as living in a garden secluded from humans. In the story of Gilgamesh, one of the world’s first epic tales, it describes the hero Gilgamesh traveling to a garden to find the Utnapishtim, the equivalent of Noah, who was saved from a great flood by building a large boat to save himself, his family, and various animals. As Utnapishtim was allowed to live forever, Gilgamesh travels to see him so that he too can find eternal life. Paradise is also described not just as a place of plants and gardens but also having precious stones and pearls. A very early tablet that discuses the domain of the gods describes it as a garden. In different mythologies and stories, potential locations of the gods could be in Mesopotamia, Dilmun (now Bahrain), or in Lebanon. While it is debatable what the region was or where it is in the minds of the Sumerians, it is clearly associated as a peaceful and beautiful setting where the gods reside. 
This concept of garden and a sacred place for the gods continued from the 3rd to 1st millennium BCE. In fact, very likely temples built during this time often had gardens within their compounds.  Although these gardens did not preserve, we often see large spaces between the physical temple structure, in this example a ziggurat to the god Marduk at Babylon, and an enclosed space with a large wall (Figure 1). This could suggest that the space between the temple structure and wall was a garden that likely represented the sacred dwellings of the gods and the holy structure inside was the inner sanctuary where the god resided. Additionally, in this garden the concept of a sacred tree is developed in Sumerian mythology. This likely is similar to the Tree of Life found later in the Bible (Figure 2).
The word “paradise” derives from an Akkadian and Persian word (pardesu is Akkadian) and (paridayda is Old Persian).  The term seems to specifically deal with structures or enclosures, perhaps associated with the walled gardens of temples discussed earlier. Soon, however, these gardens began to be found in other areas, including palaces or as pleasure gardens for royalty. The concept of gardens in Persia continue and are spread to the different Persian empires, such as the Achaemenids, Parthians, and Sassanians, who eventually influence Islamic states and empire. We can still see these gardens as they were envisioned by the Persians today (Figure 3).
With the arrival of the Greeks in the Near East at the time of Alexander the Great, the Akkadian/Persian term is utilized by the Greeks, who now associate this term as a garden with animals. This perhaps reflects the change that these gardens underwent, from generally being associated with temple architecture to also becoming royal parks enclosed in areas for the king. This concept of royal garden then develops further in Rome and spreads to Europe.
For the developing religions of the 1st millennium BC and later, in particular Hebrew and Zoroastrianism, the concept of paradise begins to develop. We see in the Hebrew Bible the story of Genesis most representing what this paradise looks like, as a place where pre-sinful Adam and Eve resided along with animals and the Sacred Tree of Life and Tree of the Knowledge of Good and Evil. Early Christianity and Islam also develop concepts of paradise as gardens that the righteous will dwell in.
Modern usage of paradise shifts between an earthly place or heavenly realm. Interestingly, however, the concept of perfection, first displayed by the Sumerians, is retained. That perfect was demonstrated as gardens, with animals and precious stones. In essence, an idealized setting that still dominates our concepts of a sacred place. This is also true for more secular reasoning, as gardens or trees are often used to describe areas many cultures consider as a type of paradise.
The road that eventually forms our religious and secular understanding of paradise seems to have an origin in ancient Sumer, where gardens are first descried as the sacred dwelling place of the gods. That mythology had a practical part in developing gardens in temples and later in palaces and royal parks. In fact, this is also the origin of our modern garden parks, although these have now become more secular in concept. Nevertheless, the Sumerian, Akkadian, and Persian concepts of paradise begin to influence the major religions that we have today. Those religions, in turn, influence more secular concepts of an idyllic place, often having trees or some seclusion.
- For more on gardens and Sumerian beliefs, see: Kramer, Samuel Noah. 1995. The Sumerians: Their History, Culture, and Character. 12. [pr.]. Chicago: The Univ. of Chicago Press.
- For more on the Epic of Gilgamesh, see: Sandars, N. K., ed. 1977. The Epic of Gilgamesh. Revised ed., incorporating new material. Penguin Classics. Harmondsworth ; New York [etc.]: Penguin.
- For more on this early tablet from c. 2600 BCE Kish, see: Barton, George Aaron. 1918. Miscellaneous Babylonian Inscriptions. Yale University Press. p. 52.
- For information on the location of paradise in the minds of Sumerians, see: Luttikhuizen, Gerard P., ed. 1999. Paradise Interpreted: Representations of Biblical Paradise in Judaism and Christianity. Themes in Biblical Narrative, v. 2. Leiden ; Boston: Brill.
- For more on temple gardens, see: Wiseman, D. J. 1983. “Mesopotamian Gardens.” Anatolian Studies 33 (December): 137–44
- For more on the Tree of Life, see: James, E.O. 1966. Tree of Life: An Archaeological Study. Studies in the History of Religion. Brill.
- For more on the origins of the term "paradise" and its meaning, see: Bockmuehl, Markus N. A. 2010. Paradise in Antiquity: Jewish and Christian Views. Cambridge [u.a.]: Cambridge Univ. Press.