Materials: The Most Important Engineering?

I'm watching “Ancient Discoveries: Machines of the East” on Discovery and as usual, there's some amazing things those ancient inventors came up with. I just saw a device that pours a fixed amount of water at a fixed interval. It used a siphon and a float based valve like that in a modern toilet. The show said this showed an advanced knowledge of differential pressures, which is used today to make jet engines. Was the only thing stopping them from making jets a lack of the materials that could withstand those forces?

There's seems to be a first key invention that starts a field of science/engineering, like the discovery of the wheel to mechanics, electricity to electronics, etc. But beyond that, could it all be a matter of making the “things” of your discipline out of lighter, stronger, or other interesting materials?

This idea is just off the cuff, I'd like to hear some comments either way.