Lean principles evolved from scientific management theories that viewed workers as lazy and lacking initiative. Deming introduced a humanistic approach in the 1940s, respecting workers and valuing continuous improvement. Lean principles focus on eliminating waste, respecting people, and continuous improvement through principles like seeing problems visually, limiting work-in-progress, and making processes policies explicit. Methods like Toyota Kata, kanban, and classes of service aim to improve flow and respect people.