Scale matters. When it changes, other things change as a function of it, often in unpredictable ways. Emergent properties are system characteristics that come into existence as a result of small and simple units of organization being combined to form large and complex multi-unit organizational structures. One can know everything there is to know about the original simple units and yet be unable to predict the characteristics of the larger system that emerges as many units come together to interact as a larger whole.
For instance, knowing everything about an individual cell sheds no light on the behaviour of a sophisticated multicellular organism. At a higher level of organization, knowing everything about an organism does not predict crowd behaviour, the functioning of an ecosystem, the organization of stratified societies, or the dynamics of geopolitics as societies interact with one another. The complex whole is always far more than just the sum of its parts.
Human social organization is particularly flexible when it comes to changes in scale. It can function in a myriad forms – from simple, generalist tribal associations, where everyone knows everyone else and interactions are grounded in established personal relationships, to the most complex, specialized and hierarchical imperial civilizations, where emergent connections and institutional structures must inevitably transcend the personal. Nicole Foss theautomaticearth.com