1. Why do you believe what you believe? What would change your mind?

I think polyamory is a net negative for society because it makes it harder to form the strongest kinds of relationship commitment which generate the most value for the couple and society. (Note that marriage is the social institution for blessing these commitments, not the commitments themselves.) At the romantic end, this is about crossing oceans to be with a partner. At the practical end, this is about a joint commitment to spend decades paying off six figures of mortgage debt on a shared home. And above all, it is about the commitment to raise a child together.

There are three main reasons for this:

  • Polyamory requires a huge amount of work (the amount of communication in a polycule scales roughly as the square of the size of the polycule), to the point where polyamorists joke that it would be impossible without modern online co-ordination tools like Google Calendar. This work is difficult, and the consequences of getting it wrong are dire – the Bay Area rationalist/polyamorist community fills my news feed with mating-related drama every year or so. (No, most communities of smart geeky people don’t do this.) I see no reason to believe a community with an average IQ below 115 could make polyamory work at all.
  • Polyamory makes it too difficult to negotiate the terms of joint commitments, particularly ones involving money. This is hard enough to do under monogamy (we don’t let people negotiate prenups without lawyers for a reason) and multilateral negotiations are an order of magnitude harder than bilateral ones. And once you reach a solution, the whole thing is up for renegotiation every time a metamour joins or leaves.
  • The strongest relationships (and the only ones that have any business bringing children into the world) aren’t 50-50, they are 100-100. (To use the technical anthropological term, strong babymaking relationships are based on communal sharing). You can’t have this kind of relationship with multiple people except in the rare case where your partners are as committed to each other as they are to you. In a world where giving more to partner A means shortchanging partner B, relationships are pulled towards equality matching or (heaven forfend) market pricing.

The main thing that would change my mind is evidence that polyamorists were raising children to adulthood in stable two (or more) parent households with an equal or higher success rate than monogamists with the same level of IQ and SES.

2a. A monogamous person is jealous of their partner (for example, because they’re afraid their partner has a romantic interest in someone else). In a healthy relationship, what would happen next?

Assuming that there isn’t some objective fact justifying the jealousy, nothing. We’re adults.

2b. A monogamous person has a crush on someone other than their partner. In a healthy relationship, what would happen next?

Nothing. Monogamy means that you don’t act on such crushes – that’s the whole point.

2c. A polyamorous person gets an STI. What typically happens next?

Unless caught early by testing (which it won’t be if everyone involved has an IQ circa 100 and a normal attitude to intoxicated sex) then the STI spreads through the polycule. This may or may not result in relationship-ending drama. If the STI in question is herpes, HIV or antibiotic-resistant it also results in a lot of morbidity.

2d. A polyamorous person hates their partner’s other partner (their metamour). What typically happens next?

A lot of unnecessary drama, followed by one or both of the metamours ending their relationship with the shared paramour.

2e. A polyamorous person has a date scheduled with their primary partner, but their secondary partner is in the hospital with an emergency and needs support. What typically happens next?

Emergency in-patient admissions are sufficiently rare and important that you can go to the hospital without disappointing your primary. The question gets harder if you use something less drastic – perhaps the secondary has just had root canal surgery and wants a hug.

3. What would happen if 90% of people in a society were polyamorous? (You may assume they all practice one style of polyamory, or different styles.)

I don’t think 90% of a society being polyamorous is possible. I don’t even think that 90% of the population can cope with monogamy without a level of social enforcement that no longer exists, and polyamory requires more intelligence, emotional intelligence, and conscientiousness to make work than monogamy does. In practice 90% of the population claiming to be polyamorous means that some large percentage are failing to ensure open and honest communication among metamours etc. and are therefore actually doing promiscuity and not polyamory. The negative consequences of promiscuous lifestyles (primarily but not only STIs and bastard children) are well-known and do not need repeating here.