What is the physical evidence that Waknuk had an earlier civilization?

In "The Chrysalids" by John Wyndham, physical evidence of an earlier civilization in Waknuk includes remnants of technology, such as ruined buildings, machinery, and artifacts buried in the ground. The presence of these remnants suggests that a more advanced society once existed before the current, more primitive way of life. Additionally, the characters' encounters with these remnants highlight their ignorance and fear of the past, reinforcing the theme of regression and the consequences of strict societal norms.