[I once again need to state that I am not responding any person or recent event. But remember the rule of subtweeting: if you see yourself in some negative description but are not explicitly named, you can just keep that to yourself.]

There is a long debate about the effects of birth order on stable personality traits. A recent article in PNAS¹ claims the effects are near null once proper controls are in place; the commentary it is paired with suggests the whole thing is a zombie theory. Anyways, one of the claims I remember hearing was that older siblings were more likely to exhibit subclinical “Dark Triad” (DT) traits: Machiavellianism, narcissism, and psychopathy. Alas, this probably isn’t true, but it is easy to tell a story about why this might be adaptive. Time for some game theory. In a zero-sum scenario, if you’re the most mature (and biggest) of your siblings, you probably have more to gain from non-cooperative behaviors, and DT traits ought to select for said behaviors. A concrete (if contrived example): you can either hog or share the toy, and the eldest is by more likely to get away with hogging.

I wonder whether the scarcity of faculty positions—even if overstated (and it is)—might also be adaptive for dark triad traits. I know plenty of evil Boomer professors, but not many that are actually DT, and if I had to guess, these traits (particularly the narcissism) are much more common in younger (Gen X and Millennial) cohorts. Then again, this could be age-grading, since anti-social behaviors peak in adolescence and decline afterwards.

Endnotes

1. This is actually a “direct submission” (i.e., reviewed as normal), not one of those mostly-phony “Prearranged Editor” pieces. So it might be legit.