Cosmogonies usually take for granted the existence “from the beginning of time” of primal matter, or even of the world itself, which is then shaped into a recognisable form either by the action of cosmic forces or by creator deities. Certain images of the uncreated cosmos often recur in different traditions: it may be represented as a void, as a state of chaos or of unformed elements, as a primeval sea, or a “cosmic egg” containing all things in embryonic form. Creation myths may reflect the environmental circumstances of a particular society. In Mesopotamia, the land between the great rivers Tigris and Euphrates, the development of irrigation systems and the fear of the sudden flooding that occurred periodically were from the earliest times a major feature of life; and accordingly the action and control of the waters plays a major role in Sumerian mythology. The primeval sea, personified by the goddess Nammu, is the source of the gods and the cosmos; and at one stage the gods decide to destroy their human creation by sending a deluge. (In many myths the creation of man and the evolution of human society are soon followed by a cataclysmic fire or flood sent by the gods.)
The processes by which the world is formed include the moulding or coalescing of elements, particularly water and earth; a struggle between supernatural powers; the sacrifice of a primal being (for example a giant or world-serpent); the incubation of the “cosmic egg”; or the uttering of a divine “word”. Where primary creation is ascribed to deities, such as the Greek Uranus (sky god) and Gaea (earth goddess), these tend to become hazy, remote figures in later mythology, and stories recount their overthrow by their own offspring: thus in the Greek tradition, Zeus succeeded his father Cronus and grandfather Uranus to become undisputed head of the Greek pantheon. Many traditions, however, do not ascribe creation to individual deities. In African mythology a cosmic egg hatches to release spirits called Nommo, who then set about the creation of mankind. Both “personal” and “impersonal” creative forces occur in Egyptian mythology: elemental energies were personified by four divine couples, who fused to form the cosmic egg; from this the sun god was born. Later the sun god was worshipped in the figure of RA, who engendered a pantheon of high gods (known as the Nine Gods of Heliopolis) by eating then spitting out his own semen. The motif of self-fertilisation by a creator deity occurs widely: his offspring may then, through an incestuous sexual union, give birth to other gods, creating a pantheon based on family relationships. The most famous such “family tree” is the ancient Greek one, centring on the offspring of Zeus by many goddesses and mortals.
Creation myths often contain the idea of separation or distinguishing (this function also belongs to solar deities, who, like the light of the Sun, reveal the true form of things). Thus the elements that constitute matter are made distinct; in ancient Egypt a mound of land was believed to have risen from the primal waters; and in the biblical Genesis story, Yahweh's creation of the world is described mainly in terms of “dividing”. Alternatively, the raw material for making the world may derive from a specific source. A widespread Native American myth tells of the descent into the depths of the ocean of an “earth-diver”, an animal—often a turtle—who brings back mud from which the world is fashioned. In Indian Vedic tradition (see Veda) the body of the primordial man, Purusha, is dismembered to provide material for the world and everything in it. A similar theme occurs in the Norse myth in which the primal giant Ymir was killed by Odin and his brothers, who then make the sky out of his skull, the earth from his body and the sea from his blood.
The process of creation is sometimes perceived as belonging to a mythic past; often, however, it is seen as a continuing cycle of creation and destruction, as in Hindu tradition or in the Mesoamerican belief in the “Five Suns” that governed successive worlds. Since the 19th century, Western thought has been accustomed to equating the passage of time with the idea of material progress; but in mythic history the earliest era of the world is usually the closest to perfection—a Golden Age or Garden of Eden—with later phases showing the progressive degeneration of the world as it grows more distant from the original creative impulse. Cosmogony myths generally culminate in the creation of humankind, after which point the mythic cosmos comes to resemble the inhabited world of human experience. The earliest humans are often thought to have been of extraordinary stature and longevity and to have been much closer to the gods, and in many traditions the story-cycles associated with demigods and heroes are a richer source of myth than those involving the gods themselves.