Symbiosis and Dependency
Bacteria in a community often cannot survive alone. They trade metabolites, complete each other's broken pathways, and lose genes they no longer need because a neighbour supplies the product.
The human parallel
Long partnerships change both people. Over time you divide the labour, drop the skills the other person covers, and become genuinely harder to separate.
Why it matters
Dependency is a real biological outcome of long relationships, not a metaphor. Species lose capabilities they no longer need alone.
What we can say
Each claim carries a confidence rating, a caveat, and the papers it rests on.