How does the time loop in Predestination get initialized?

In Predestination starring Ethan Hawke, the idea is plain and simple. However, I do find something very hard to digest:

How could the loop about Ethan Hawke the time travel agent, could meet himself and then conceive himself without some sort of help to initialize the loop?

What I want to say is that, in the first loop of the story, there is only one Ethan Hawke. He then travels back in time and after meeting his past self, he gives birth to himself. But who was responsible for the birth of the first Ethan Hawke?

As a developer this bugs me more than it should. Any theories?