[flumbaps]

I had this cool idea for a sci-fi book (I may one day write), set long after modern civilisation collapses. Humans survive but with all the readily available iron ore used up, we are perpetually stuck in a pre-industrial revolution world. Hundreds of thousands of years pass and we evolve. At this level of technology we can farm, so we're still very successful, and the biggest threats to us are diseases rather than predators. So we evolve towards having much greater conscious control over our bodies and health. Incremental changes happen, starting from an expansion of the existing placebo effect, towards a conscious ability to manage immune responses, and then further into being able to affect cell chemistry in different areas of the body. The book would follow what happens when humans evolve the ability to do genetic engineering on themselves, and the following completely organic technological revolution. (Probably ending with some gene hackers growing diamond hulled space craft and leaving to explore the galaxy.)