What ends the era of pre-history and begins the era of history?

In general, historians look at the invention of writing with the early civilizations to define what is known as "recorded history." So that when we refer to the Dark Ages, for example, we are also talking about prehistory because, essentially, nothing was recorded. This is why this period prior to the Middle Ages is called "Dark." There's a difference, however, between a culture having no writing and having no system, thus it would be a mistake to think that a culture without a writing system is not a culture. It most likely had an oral tradition. This was generally true of early hunter-gathering "nomadic" cultures prior to the advent of agrarian communities and more stable settled environments with which, eventually, developed writing systems and "recorded" history.