Interesting BBC programme In Our Time this morning about The Dawn of the Iron Age. Why and how did people start making ornaments and tools and weapons from copper and tin and lead? Because the ores were shiny, and it was easy to see how they could be melted and purified and worked. Gradually, people discovered that certain combinations of these materials (what we now call alloys) were stronger, or more malleable - hence the development of bronze.
Although iron ore was much more abundant than any of the others, it was much less attractive, and primitive people were unaware of its potential value. Even when melted, it didn't look much. Producing useful iron from this stuff was a more complicated procedure, and those tribes that first discovered the secret wisely kept it to themselves. Egyptian tombs had a few iron items, but these were probably obtained by trade or capture - the evidence suggests that Egyptians themselves did not know how to produce iron.
Could people ever have worked out how to produce iron if they didn't already have the experience of working with other metals. Would people ever have thought it worth the extra hassle of producing iron if they weren't aware of the limitations of using other metals? Is it conceivable that we could ever have had an Iron Age without having a Bronze Age first?
There is an important lesson here for innovation. Nobody should ever be satisfied with the "low hanging fruit". The only purpose of the low-hanging fruit is to get us started, to feed us and motivate us as we build ladders, so we can reach the high-hanging fruit.
Venkatesh Rao, The Disruption of Bronze
Paula Hay, Cognitive Archeology of the West