That means, if a trait is unaffected by the environment, then there's no attribution of why it developed; this is the default state.
I feel often in biology, there's a mindset of figuring out why features developed and that's great for pushing the field but it runs into a limit. Not every trait developed from a environmental pressure.
I don't agree and that's totally fine-- we have millions of gene edits from parent to child and not every change is environment-selected. Certain features can be dominant by the mechanics of genes, not due to selective pressure.
Blood types are an example of this-- they aren't major environmental pressures for why one blood type is more common than others, it mostly comes down to population mechanics.
My belief is that "spandrel" features are less selected for studies because they have a harder burden to prove; there exists no external reason they exist and this must be verified through proof by contradiction. Its a high bar to prove.
