This one's been intriguing me for a few years as a question to pose for our collective brains to muse over. I'm interested in archaeological technology without having engineering or architectural expertise, and wanted an analogy to explain how a particular extreme and spectacular form of prehistoric Scottish architecture evolved - if anyone's interested, it's the broch - and I'm fairly sure its evolution incorporated lots of minor technology advances, alongside huge engineering techniques, and I wanted a recognisable comparison to show how essential apparently tiny features would have been.

At the back of my mind was a faint memory of an article by LJK Setright - eccentric intellectual car journalist wnen I was a young'un, who argued that the invention of the car heater was a fundamental game-changer. I don't have the article any more and the detail of his arguments is too long ago to remember properly, but I think it went something like this.

Someone in 1920s had the idea of pumping heated air from the engine into the cabin. This allowed:
- people to no longer need to wear bulky outdoor clothes for warmth, so with coats and hats no longer required, seats and cabin could become more compact
- there was now an incentive to design enclosed and weatherproof cabins instead of open-sided tourers
- this meant car usage was much more attractive in all weathers
- bodywork material could evolve from permeable (to air and water) materials eg wood, fabrics into impermeable such as steel
- steel bodywork meant there was no longer a reason to build cars as a marriage of chassis to separate bodywork of whatever type and material. With both elements being steel, the design could start integrating them into unitary construction
- unitary construction allowed greater degree of industrialised manufacture and factories, replacing previous mix of machines and hand-made elements.

So cars could become more compact and therefore more efficient, a greater degree of automated machine production reduced costs and cars became more affordable and mass-market, all because of a small and trivial innovation. Obviously there were lots of other advances alongside, so a cabin heater can not be regarded as the sole mechanism to achieve all this, but the potential it unleashed to trigger so many other advances is the point LJKS was making.

Therefore is this a convincing analysis?? No doubt LJKS made it a lot better than my attempt, but what is the consensus? Or are there better candidates for the header question??

not sure if there is but that one sure has solid arguments...