In the beginning, Genesis was not a book, or even part of a book. We are so used to the ease and convenience of printing that it is hard always to remember the processes that lay behind books as ancient as the Bible.

In the beginning, a lot of Genesis was probably passed on by word of mouth. In its written form, several different styles can be detected, which suggests that the material comes from different hands, different sources, at different times. From the advent of modern literary critical scholarship until quite recently, these different sources in Genesis were identified as J, E and P. J was thought to come from the ninth century BCE, and generally calls God "Yahweh" (or "Jahweh" – hence J). E, who calls God "Elohim", was thought to come from about a century later, and P, the Priestly writer, or school of writers, was thought to be the collector or editor of the whole, adding more material of his own, after the Exile, in the fifth or sixth century BCE. On the whole, this is still the consensus, though scholars are less assured than they used to be about assigning different parts of the text to different authors.

Then, when Genesis was brought together as one collection, it was copied, over and over again, by many different hands, and translated into many different languages. No copyist was perfect and each translator made decisions, good and bad, about the best match in translating. Ancient Hebrew text did not include letters for the vowels, so a system was developed for indicating vowels above and below the consonants in Hebrew. Again, decisions had to be made, on the basis of memory and traditions of reading and repetition, about which vowels went where.

A great project to translate the Hebrew scriptures into Greek produced the Septuagint version, by about the end of the third century CE. For most of Europe, the version they thought of as the Bible for about a thousand years was the Vulgate, in Latin. Modern translations compare all the different traditions, look at varieties of manuscripts, including fragments from the Dead Sea Scrolls, and try to come up with the most reliable reading, if there are variants.

Why does any of this complex history of transmission matter? Indeed, there has been a considerable backlash among commentators recently, who argue that what really matters is the theological story that Genesis tells. But while that is certainly true, the history of how we come to have Genesis reminds us that we have Genesis for a reason. Choices were made to preserve and arrange this particular material, rather than any other possible narratives, because Genesis as it now is makes sense.

There are three blocks of narrative in Genesis: the primeval history, from creation to the Tower of Babel (Genesis 1-11), which shows the world in its proper relationship to the creator, and how this went wrong. Then Genesis 12-36, the patriarchal narratives of Abraham, Isaac and Jacob, show God's rescue plan, while the block of material about Joseph in 37-50 brings Israel into Egypt, ready for one of the most formative times in Israel's history, the Exodus.

After the Exile, when the people looked back at what had happened to them and tried to make sense of it, they either had to abandon their belief in God, or to admit that their god was less powerful than the gods of their conquerors; or else they had to discover in their history some meaning and purpose in what had happened, something that would allow them to go forward again.

And what they discovered were these magnificent descriptions of the one God, creating in freedom and with joy, maintaining a relationship with the people, however much they misunderstood and betrayed their God. They discovered their vocation, to be signs and reminders of the real purpose of humanity: to live with God and share God's work in creation. They discovered that God is not there for our use, but that we have a sacred calling to be "images" of God in our relationships with each other and the world.

Genesis belongs, first and foremost, in the history of God's relationship with the Jewish people. But just as it shaped Israel, so it has continued to shape those who find themselves living in this story, which starts with God's creation of the world. Genesis has provided definitions, justifications, hopes and inspiration. Its text has been mined for controversy, for dogma, to justify oppression and to fight against it. It has proved itself an infinitely rich resource, whose contribution to human self-definition is neverending.

"In the beginning God created …", and continues to do so.

So someone or some group of people, after the trauma of the Exile, decided to collect together various traditions and documents from Israel's past and put them together. Presumably, what we have in Genesis was not all there was. Other stories, other patterns, other descriptions would have existed. But these ones, taken together, are designed to help the people to reflect on what has happened and why.