> cambodia in 2002 had an iq of only 89 > now, we have an average median iq of 99.75 pol pot kills all the intellectuals, temporarily decreasing the average iq of the country. however when he's done, people start breeding again and more normal and above iq people are born pushing the iq average back up.  i don't really think you need an explanation beyond that op.  tl;dr - kill all the smart people and it takes a couple generations to repopulate
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