Imagine humans who have been augmented with shocks, servo-mechanisms, and sensoriums that allow them to send and receive radio and electromagnetic waves. Imagine a planet, once cool and wet and full of humans, now warming and drying and full of machines.
Humans are the vermin, the rats in the barn to be eliminated.
Now imagine a machine with a great deal of curiosity about humans, an artist who uses his art to explore the gap between organic and mechanical forms, between those who can die and those who are disassembled and then reassembled. This is the world Gregory Benford explores in this book. It is unclear in this story where the mechs came from originally. There is no indication that they were created by humans. They seem to have evolved on their own, but they have been usurping planets for some time, according to the memories of the people.