Historical anarchism isn't the same as modern-day anarchism, though. As production and distribution became more complex, different forms of organization came about to suit the level of the productive forces, giving rise to class society. We cannot use historic hunter-gatherer anarchism as proof of modern-day anarchism working at scale, as the material conditions are entirely different. That is, unless you're talking anarcho-primitivism, in which case I think being able to manufacture things like insulin is necessary.