When you look for someone to marry, you’ll care about many things: Are they smart? Healthy? Kind? Funny? Educated? Employed? And are they, like, wicked hot?
But ask your parents. They won’t say that hotness is irrelevant. But they’ll probably care about it less than you do. (If you trust peer-reviewed research more than common sense, I refer you to Perilloux et al. 2011, Apostolou 2015, Dubbs and Buunk 2010, or Apostolou 2008.)
This is a story as old as time. So old that it’s easy to miss that something really weird is happening here.
After all, why do you want to marry someone hot? Evolution made you that way because hotness is a proxy for good genetics. Your genes want you to reproduce with someone hot so that you will produce lots of kids (who will have lots of kids). Your parents care who you marry because evolution tuned them to help you reproduce your genes (which are also their genes).
So… that seems confusing. Don’t you and your parents have the same priorities? Why would you give such different weights to different characteristics of who you breed with?
Theory 1: Strategic conflict
One theory, suggested by Trivers (1974) is that parents and children don’t quite want the same things. Your parents share an equal number of genes with all their grandchildren. But you share twice as many genes with your kids as with your nieces and nephews.
If you marry a doctor, maybe they’ll help your niece with tuition or convince her to major in pre-med instead of comparative Sanskrit opera studies. But if you marry someone with amazing genes, your niece will get none of them.
So maybe your parents care more about the social status of who you marry because that has benefits for all their grandchildren. You care more about attractiveness because you give twice as much weight to your own kids.
Theory 2: Older and wiser
Or maybe that theory is way too clever. Maybe it’s just that people change as they age due to hormones and brain plasticity and life experience and whatnot. The “conflict” may exist in theory but isn’t a significant part of why your parents are less obsessed with the your mate’s cheekbones than you are.
Which of these theories is right? I have a few observations.
Older people are different
Older people give different advice to everyone about everything. Sure, they might point out the advantages of marrying someone who’s boring but reliable and rich and from a good family. But they’ll also tell you to take care of your teeth and wear sunscreen and save for retirement and be kind to yourself and maybe try listening to Depeche Mode or The Police.
I have no evidence for this, but older people may also give a lower priority to looks when choosing a partner for themselves. (Speculative)
This seems to point in favor of Theory 2. Except that evolution loves “hacks”.
Suppose, long ago, everyone just wanted to mate with hot people. If their kids asked them for advice, they’d just say to put on some tight-fitting pants, find the hottest person you can, and “accidentally” trip in front of them.
Now, imagine a mutation. If someone has it, they still choose hot people to mate with, but they advise their kids to consider wealth. According to Theory 1, this will help that person reproduce their genes, so the mutation will spread.
How would this mutation work? There are lots of possibilities:
- Maybe it makes people hypocritical—they choose hotness for themselves but advise others not to be superficial.
- Maybe it makes people’s brains change as they age—they value hotness less when older.
- Maybe it changes how people learn from life experience in general—so that, among other things, by the time your kids are reproducing, you’ve concluded hotness really isn’t so important after all.
Sure, all of these will have other effects in other contexts. But so what? Evolution’s first priority is reproduction, so these would spread anyway.
So maybe strategic conflict is the reason that older people give different advice to everyone about everything. Evolution did this so that you’ll encourage your kids to mate in a way that will help out their nieces and nephews, and all the other effects are incidental.
Kids care much more about hotness
Whether they admit it or not, I’m convinced your parents do want you to marry someone hot. They just figure—probably correctly—that things would get weird if they talked to you about it. Still, they care a lot less than you do.
This also seems like a problem for the strategic conflict theory. Just think about it: If you marry someone rich, how much of those benefits really spill over to your other nieces and nephews?
Let’s make a simple model:
You are looking at a potential spouse who has two attributes,
Looks only benefit your kids, while status also benefits your nieces and nephews. So there are three kinds of benefits, namely
(LOOKS → YOUR KIDS),
(STATUS → YOUR KIDS), and
(STATUS → NIBLINGS).
(A “nibling” is a rising term for a niece or nephew.)
If your parents calculate how much this person enhances their reproductive value, they would have three terms:
(VALUE TO PARENTS)
= (LOOKS) × (LOOKS → YOUR KIDS)
+ (STATUS) × (STATUS → YOUR KIDS)
+ (STATUS) × (STATUS → NIBLINGS)
The reproductive value of this person to you is the same, except giving half as much weight to nieces and nephews:
(VALUE TO YOU)
= (LOOKS) × (LOOKS → YOUR KIDS)
+ (STATUS) × (STATUS → YOUR KIDS)
+ (STATUS) × ½ × (STATUS → NIBLINGS)
Do you see the problem? How large can
(STATUS → NIBLINGS) possibly be compared to
(STATUS → YOUR KIDS)? Surely the status of someone you marry benefits your own kids a lot more than your nieces and nephews?
This suggests that even if a strategic conflict existed, your parents should give only a little less weight to hotness than you do. But they seem to weigh it a lot less, more than the reproductive incentives could explain.
(Aside: You might object that status would have splashed over onto extended family more in our evolutionary past before our lives became so atomized. If so, my compliments on making a strong argument that I can’t refute. But no matter: I’m going to argue that even if there was a small impact of status on nieces and nephews, then Theory 1 could still be true.)
Conflict happens on the margin
Say we’re driving across a desert. You’d like to head straight north, while I’d like to go a few degrees west of north. We don’t have a great vibe going as regards communication, so we settle our dispute by each childishly tugging at the steering wheel. Even though we want to go to almost the same place, we’ll end up each pulling as hard as we can.
Now, let’s go back to the world where everyone values hotness equally for themselves and for their kids. And suppose that there is some strategic conflict, meaning that your parents’ interests are maximized by you giving hotness a lower weight than your own interests would dictate. To be concrete, suppose your parents would like you to give hotness 1.2x less priority.
What strategy should your parents take? Suppose they try, “You know, sweet pea, looks are 1.2x less important than you think they are.” Here’s what would happen:
- That advice would go into your brain.
- It would do battle with hormones that have been playing this game for millions of years.
- The hormones would win.
If they say 1.2x, you’ll reach a “compromise” position of something like 1.02x. Thus, the best strategy for your parents is to tell you that looks are much less important than you think, so that after down-weighting, you land at 1.2x.
But if your parents are doing that, then your best strategy is to care even more about looks. But that incentivizes your parents to give even more extreme advice, et cetera. In this way, small differences in incentives can lead to very large differences in what you care about because you’re both trying to control the outcome after compromising.
In my view, this is a strong defense of Theory 1. Even if status has a tiny effect on nieces and nephews, you might still have a huge disagreement with your parents about how much it matters.
Older and wiser happens on the margin, too
Here’s an argument against the “older and wiser” theory: Say we agree that people change as they get older. Why would this produce conflict? If you and your parents have the same goals, why are you arguing?
Well, we need to apply similar thinking as in the previous section.
Now imagine again a world where humans only care about hotness, and suppose who you marry has no effect on your nieces and nephews, so you and your parents have the same interests. But then evolution looks around and says, “Wow, status is awesome! All these resources for the kids… Boy, it would be helpful to take that into account!”
How should evolution accomplish this? Here are two options:
- It could try to make you attracted to people who have status.
- It could make your parents steer you towards people who have status.
(Yes, of course, it could do both, but bear with me.)
Which of these would work better? Well, maybe evolution would notice that you are young and stupid. You don’t know how the world works and have no idea about the social structure in your village. But your parents are old and wise.
If so, then evolution would decide that status judgments should be left up to your parents. Evolution would basically leave you to continue being attracted to hotness, but not fight your parents so hard that they have no impact. (In most cultures parents do exert substantial control over children’s marriage choices. (Apostolou 2010))
So this argument isn’t that strong either: Evolution might have chosen “have parents and kids argue bitterly” as the best mechanism to combine the information that you and your parents have.
At first, it seems odd that you’d disagree with your parents about who you’d mate with.
The “strategic conflict” theory is that you care more about hotness because good genes only help your kids, whereas social status helps the rest of the family. The “older and wiser” theory says that those externalities aren’t important, and it’s just that people just give different advice as they age.
At first, both of these explanations seem hard to reconcile with what we see in the world. But once we remember that evolution is tuning everything for effects on the margin they look much more plausible. Very small starting differences (in incentives or wisdom) can produce huge differences.
So which theory is right? Or at least, which is more important? I’m not sure, and it’s not obvious what data could resolve the question.