How do you know that Adam and Eve were the first people alive?

It is not possible to know that Adam and Eve were the first people alive. In fact, the distinguished biblical scholar, Raymond E. Brown, says that for parts of the story in Genesis 2:4b-3:24, Adam is not an individual male but a figure representative of humanity. In other Words, the author of this story did not even intend it to be taken literally. The story of Adam has a number of strikingly similar predecessors in older civilisations in the Middle East. In the Epic of Gilgamesh, the king was an oppressive ruler, so his constituents appealed to the gods, who create a nemesis, Enkidu. In some of the parallels with the later story in Genesis, Enkidu was created naked in the wilderness, and was tempted by a harlot, who educated him about sin and taught him to wear clothes.