[Legend of Korra] How did people bend the elements after the era of the lion turtles?

That’s a question I’ve had for a very long time. In the episodes, “The Beginnings”, bending was only given to humans so that they could defend themselves against the spirits that have invaded their world. At the end of the episodes, Wan closes the spirit portals and sends the spirits back to their realm. So my question is: How did people bend after the era of the lion turtles? There were no spirits for humans to protect themselves against. Did the lion turtles still gave them bending as a kind gift or so that humans could defend themselves against other humans?