Many people have made the observation as time goes on society slides evermore left. One of the primary questions for any political scientist would be trying to figure out what causes this trend.
Arctotherium, using General Social Survey data, looked at white Americans born between 1920 and 1990. He found that their views shifted about 1.511 standard deviations left. He made these calculations trying to argue against the mutational load hypothesis.
The MLH comes from self-described Socio-biologist Joseph Bronski.
His argument is summarized as follows.
First, people who have more conservative views tend to have more children. When we do the math, this pushes views about 0.076 standard deviations toward being more conservative each generation. Scientists call this selection pressure (Bronski, 2023b).
But there's a larger force pushing the other way. When fathers are older when they have kids, their children tend to be more leftist. Scientists calculate this using three numbers: the average age fathers have kids (30), how much these ages vary (7 years), and how strongly father's age relates to political views (0.07). Multiplying these together (30 × 7 × 0.07), we get a push of 0.22 standard deviations toward being more leftist each generation. This is called mutational load (Bronski, 2023a).
When we combine these forces (0.22 pushing left minus 0.076 pushing right), we get 0.144 standard deviations moving left each generation. This matches almost perfectly with what we actually see happening (0.15) (Bronski, 2023b).
Now these genetic effects show up most stronger as people learn about politics. For what people euphemistically call low-information voters, genes explain about 57% of the variation their political views. But for people who know a lot about politics, genes explain up to 74% (Kalmoe & Johnson, 2021). This means the environment (everything that's not genes) only explains 26% of the variation in their views. And we know that this is a lowball estimate, because the metric Kalmoe and Johnson used is the WP-conservatism scale which has realistically poor psychometric properties (Bronski, 2023a).
Using this information we can do some math to see how unlikely it would be for just the environment to cause such big changes. For regular people, where the environment explains 40% of views, we:
Take the square root of 0.4, which is 0.63
Divide our total shift (1.511) by 0.63
This gives us 2.39 standard deviations from what we'd expect
The chance of this happening randomly is only 0.84% (p = 0.0084)
For politically knowledgeable, the political elite, the the environment only explains at most 26% of the variation in their views.
We can do a similar analysis because we know elites and commoners have similar distribution in view once adjusted for gender, status and races, all highly heritable traits.
In a study from the late-1980s, Lerner, Nagai & Rothman recorded something curious: America’s elites weren’t very ideologically divided from wider society. Or this would be true, if Jews weren’t included in the sample. This split is very cleanly visible:
Thus, we:
Take the square root of 0.26, which is 0.51
Divide 1.511 by 0.51
This gives us 2.963 standard deviations
The chance of this happening randomly is even tinier - just 0.152% (p = 0.00152)
Over the whole 70-year period, the effect was huge by social science standards - about 1.93 standard deviations (or about 0.0276 per year).
What does all this mean in everyday terms? The biggest reason political views have changed over time probably comes from genetic changes. This shows up most clearly in people who know a lot about politics, the political elite.
Even though some forces (like conservative people having more kids) push one way, the overall genetic push toward more leftist views seems to be stronger (Bronski, 2023a). The numbers make this especially clear among people who follow politics closely - the math shows it would be almost impossible for these changes to happen just by chance or changes in society.
If we want to understand how political views change over time, we need to pay attention to genetics and the possibility the ML is the cause of leftward slide of history.
I used to be really into Bronski a couple of years back. Thanks for reminding me of him! I quite his work and your article as a fellow disagreable autist.
I used to be really into Bronski a couple of years back. Thanks for reminding me of him! I quite his work and your article as a fellow disagreable autist.
But why does the yeti swim doggy paddle?