[dragonwriter]

> I don't think that controlling for variables can produce a conclusion of causation.

Controlling for variables can rule out alternative causal relationships (shared causes between A and B rather than A causes B) as explanation for correlation, but can't rule out coincidence. They strengthen the case for these plausibility of a causal explanation.

[misp]

In my view, controlling for a variable X doesn't directly strenghten a causal claim, but allows to "rule out" another plausible explanation. In a way it shows that the observed effect is not accounted for, even if we take X into account, which means that it could be that the father's age influences filial geekiness. It could still be the case that another variable (that was not controlled for) accounts for the effect.