Are you sure your digging deep enough? I have seen plenty of cases where different fields seemed to share a theme. But, the details always diverged on closer inspection, limiting the value of the comparison.

To stretch an analogy stacking blocks seems like you can add the heights, except the weight of the stack deforms them, so addition is misleading.

At some level one can think of anything as unique, but it's often more useful to consider in what way two (or many) things are similar.

We've got a bit of a dialectic:

Thesis -- The map is not the territory.

Antithesis -- There's nothing so practical as a good theory.

Synthesis -- Use a subway map when catching the train, use a topographical map when doing flood planning, etc.

Taking it back to programming, all abstractions are leaky in some way. A good software engineer uses the right abstraction for the task, knowing that it might be wrong for a different task.

Human themes (archaeology, art, architecture, urban development, etc) share the commonality of the human. As we learn more about general themes driving our psyche and human groups general themes start to emerge. Of course, the emergent behavior of human societies is really complex. I like Noel Harari's "Sapiens" as he really strives to find the high level themes in humanitys development.

IMO, if a topic sounds overtly complex and focuses on a legion arbitrary seeming minutiae and, most crucially, you can't find the empiric or mathematical root cause for this complexity it's likely the direction of study is more or less bogus and based on academic eminence rather than evidence.

Urban development really is it's own thing dominated by transportation systems, wealth, waste management etc. The complex math is vital and independent from other human constructs. Architecture was often influenced by the tax code, climate, material property's etc so again the details really are important and separate from everything else.

Now, sure the boundarys around a field gets fuzzy and sculpture and architecture are both influenced by the human visual system so there is overlap. But, that's not a shared theme that's D.C. and Baltimore being next to each other and sharing a few suburbs at one end, but not all suburbs.

Example: kelvin-helmholtz instabilities, applicable in dynamics ranging from vascular systems to cloud formations to interstellar nebulae, and so much more.