Not sure if that's true, what are your reasons for believing that? Are you saying we couldn't have invented the machines we used if we took safety measures along the way (e.g. having guards on machines that chopped of arms and legs)? Perhaps progress would have been slower -- since rather than just using the saw, you'd need a saw with a guard and emergency switch -- but it seems like if humans were more circumspect, we would have the industrial revolution, but more deliberate and controlled. Agreed it probably wouldn't have been "overnight factories in every city", but then again, you probably wouldn't have many of the externalities we're still learning about and paying for?