[nitrogen]

Arguing that things come about as combinations upon combinations of small, 'not completely new' inventions is begging the question. When you compare the state of human affairs in 5000 BC with the state now, you can't possibly mean that no 'completely new' things have been created.

This is like measuring the slope of a line across a very large span, and saying that because the change in Y value is so large, there must be a discontinuity.

This is the same problem as e.g. distinguishing species in biology....

I don't think biology is the best place to look for guidance when creating an epistemology or taxonomy of technology. The concept of species is important in biology, because it's a strong signal as to which organisms can successfully interbreed. In technology, nearly any two (or more) ideas can be combined.