undefined | Better HN

0 pointsandrewflnr8mo ago0 comments

I hadn't heard the term "spandrel" before, especially not in this context. Makes sense, though. https://en.wikipedia.org/wiki/Spandrel_(biology)

0 comments

3 comments · 1 top-level

rirze8mo ago· 2 in thread

I personally dislike the definitions here-- traits and genetic changes are, by default, unattributed to external pressures. They don't "arise" from the environment, rather the environment selects for traits through survival/reproduction, if applicable.

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.

andrewflnrOP8mo ago

Technically yes, kind of, but if a feature is truly unaffected by the environment, then there's no particular reason it would get fixed, and you have to make the rather shaky assumption that it became widespread purely by chance. Most features have some cost, and the simplest explanation for that feature being widespread is that it has some counteracting benefit that leads to it being selected for. That's a reasonable first hypothesis, to say the least, which means the "spandrel" hypothesis makes sense as the less common special case.

rirze8mo ago

> Most features have some cost

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.

1 more reply

j / k navigate · click thread line to collapse