Curves in Nature vs. Curves in the Built Environment

Back to the question of natural curves, which I touched on lightly the other day. Let's have some fun looking at a natural curve vs. a human-built curve. I just want to brainstorm about their characteristics, their functions, and their constraints.

Here's the natural curve of the day, the branches of a Saguaro cactus.

Characteristics: Acute angles, curve dominated by upward sweep of the branch.

Functions: Weight-bearing, growth upward, photosynthesis.

Constraints: Weight, tissue available for building, exogenous constraints like heat and dryness.

Let's see what I can find in a human-built shape that resembles this...

The arches seem like a kind of inverted branch. Obviously there are differences as well as similarities...let's explore.

Characteristics: Symmetrical, "branches" downward-facing.

Functions: Weight-bearing, decoration, shelter

Constraints: Weight, design, cost, others?

I'm not a structural engineer or an architect. Maybe you know someone who is. What kinds of comparisons would they make between these two curves? Is it worth discussing further?