Is there a difference in heritability of antisocial behavior that's sexed?
Do men inherit more accurately?
Is the heritability a greater effect on boys than it is on girls?
Generally, no, but there's one exception that I want to come back to.
So what we see is that the genes that are associated with antisocial behavior in boys also affect girls.
If you're female and you have a fraternal twin that's a male sibling, then his antisocial behavior predicts your likelihood of manifesting it that the same liabilities are reflected in the same way.
So the same genetic liabilities make you more likely to be physically aggressive, they make you more likely to be relationally aggressive, they make you more likely to be substance using.
They make you more likely to be risk taking.
It's just for everything the mean for men, the average for men is shifted up.
Oh, so the same impact would have a Sorry, the same raw materials would have a greater impact in real life.
Yeah, yeah, yeah.
Yeah.
The same way as women commit suicide.
Sorry, women attempt suicide more than men, but men commit suicide more than women.
Yeah.
It's their ability to enact... violence, antisocial stuff tends to be greater.
So it's magnified, right?
Interesting.
And so, you know, part of that is around social opportunity.
Like for many years, you know, women were very discouraged from drinking.
Very different were discouraged from smoking.
So you saw a big sex difference in smoking and drinking.
Now it's more socially acceptable for women to smoke and drink.
And so that average difference has narrowed, and it's the same genes that seem to be involved in both.
The exception there is that most of our current studies have focused on what are called the autosomes.
So we have 23 pairs of chromosomes.
One pair is the sex chromosomes, XY or XX, and typically developing children.
And then the other 22 pair are the same across sexes.
And nearly all of our contemporary studies have focused just on those 22 pairs of autosomes for kind of boring technical reasons that I'm not gonna get into.
We're just now really diving in to the X chromosome to see.
Is there something about the X chromosome that might have specific effects on antisocial behavior?
And the reason why that's interesting is because men only have one x, whereas women have two, and so men are much more vulnerable to the effects of a genetic variant that's x linked, because they don't have another copy to compensate.
Oh, that's so cool.
So that's why colorblindness, for instance, is much more prevalent in men versus women, because it's an X chromosome linked genetic variant.
That is so sick.
So the reason why we think the X chromosome might be important And again, just to back up a second, most of what we study in our lab is what we would call common genetic variation.
So these are genetic differences between people that exist in at least 5 sometimes people say at least 1 of the population.
The thing about common genetic variants is that they're common, which means that they are likely to have a relatively small effect in isolation.
Because if they had a big effect, evolution would make them not common, would weed them out very quickly.
So you have this trade-off between how common is a genetic variant and how big of an effect, how powerful it is.
So what we're looking at is lots of common genetic variants, each of which have a tiny effect, but if you add them all up, then you get an appreciable effect, one that's meaningful.
But there are studies of rare genetic variants and there's one very famous study that was done in the 1990s where they looked at a rare variant on a gene on the X chromosome And that gene was called MAOA.
So your monoamines are how your neurons are talking to each other.
It's like serotonin's a monoamine, dopamine's a monoamine.
So monoamine oxidase is an enzyme that basically is like a Pac-Man eating the neurotransmitter in your brain.
And if it doesn't work well, then you get this incredible buildup of the signals that your brain ordinarily uses to communicate with each other.
Okay, so why is that important?
In this one family where they found this genetic variant on the X chromosome.
It made the MAOA enzyme not work And all the men in that family suffered from extremely serious antisocial behavior problems, whereas their sisters were completely typically functioning.
So the men?
One raped his sister, one committed arson, one stabbed his boss with a pitchfork.
Huge levels of antisocial violence in this family.
Their sisters and their moms were like, what the fuck is going on here?
Why do my sons and my brothers keep doing this and we don't have this problem?
And it's because they have two Xs.
And so if they inherited the mutation, it didn't matter, because there was another functioning version of the body.
To regress them back toward the mean kind of dosage comp, like they could compensate for it, whereas if, if you're a man and you only have one ex and you got this, you know 50 50 shot.
Which of your mom's exes are you getting 50, 50 shot?
Whether or not you were going to be antisocial, so that's a rare variant.
You know the vast majority of people who are deeply antisocial do not have this maoa.
Don't use the MAOA excuse.
They can't use the MAOA excuse.
But I think it's important for two reasons.
And one is that we think of our moral faculties as our ability to not go around stabbing our boss every time we're mad at him in moral terms, in spiritual terms or in cognitive terms, and it turns out that it's very vulnerable to disruption.
You can change one letter of your genome, that changes one gene, which changes one enzyme, and that capacity is really, if not destroyed very, very impaired.
And so the extent to which our morality is a biological faculty, I think, is very much supported by the fact that we can so profoundly disrupt it by this one change in our genome.
And the other thing that I find so interesting about this case study is that These men were in the criminal legal system in the Netherlands and no one was like oh, this must be a genetic problem.
They weren't not guilty by reason of insanity.
They weren't, you know, lacking capacity to just stay on trial.
They were indistinguishable from the rest of the offending population based just on their behavior.
And the only reason we know that their behavior was due to this genetic cause is because of the familial data that made the pattern of transmission so clear.
And I think that really brings up the question how many other people who are persistently violent in families that are persistently violent?
There might be some genetic or neurobiological explanation that we just haven't discovered yet.
Like, we just don't know that.
In the 80s, they would have considered it ridiculous.
Like ugh, this persistently violent family.
You're telling me it's because they have one gene.
That's wrong.
Like, what if it sounded like science fiction?
But that was the case for this family.
So we haven't, in modern genomics, turned our attention very often back to the X chromosome, but my lab is doing this now and I'm really excited about this project.
Quick aside, i've been using eight sleep for years and i genuinely can't imagine life without it.
Having a mattress that actively cools and heats each side of the bed is a total game changer, and the newest model, the pod 5, takes things to the next level.
It now includes a temperature regulating duvet that works with the smart mattress cover to deliver full body climate control, maintaining your ideal temperature from every angle night long.
The new base also includes a built-in speaker so you can fall asleep to ambient sound, rainfall or dr andrew huberman, whatever helps you switch off.
And with upgraded biometric sensors it now runs nightly health checks, identifying disrupted breathing, abnormal heartbeats or sudden changes in your hrv.
It now cools heats, elevates and monitors your sleep better than ever, which is why eight sleep has been clinically proven to give you up to one hour more of quality sleep every night.
And if you're still on the fence, they have a 30-day sleep trial so you can buy it and sleep on it for 29 nights and if you don't like it, they'll just give you your money back.
Plus, they ship internationally right.
Right now you can get up to 350 off the pod five by going to the link in the description below, by heading to 8sleepcom slash modern wisdom and using the code modern wisdom at checkout.
That's E-I-G-H-T sleep.com slash modern wisdom and modern wisdom at checkout.
Thank you very much for tuning in.
Ooh, a tasty morsel of a clip there for you.
Well, the full episode is available right here.
Go on.
Pass it.
