I'm intrigued that the stated IQs seem above-average (100):

"In the study, Norwegian epidemiologists analyzed ... military records. ... the researchers found that eldest children scored an average of 103.2, about 3 percent higher than second children (100.3) and 4 percent higher than thirdborns (99.0)."

103.2 more than compensates for 99.0.

Since Norway has mandatory military service http://en.wikipedia.org/wiki/Military_service#Norway , this does not refute jokes about "military intelligence".