Eh.... I come from a family of 8 kids. All of us have at least bachelors degrees, many have multiple graduate degrees, including doctorates.

> Additional siblings have lower cognitive scores than their older siblings.

One of my youngest siblings was valedictorian of a high school class of 4,000 students, got perfect scores on the ACT and SAT, was accepted into MIT and many ivy league schools and recently was incentivized to move to a new company with a $1 million bonus. He is straight up a genius.

I mean, obviously there are outliers to everything, but this study strikes me as maybe having a correlation and causation issue.