Oh, and another example, merit based immigration. The offspring of parents regress to the mean, which means smart parents have children that are smarter than average but less smart on average than their parents. Same thing for dumbs. The upshot of this is if Country A has an average IQ of 100 and Country B has an average IQ of 85, if A imports everyone from B with an IQ of over 115 all that will be accomplished in a few generations is to lower the average IQ of both countries.
Oh, and another example, merit based immigration. The offspring of parents regress to the mean, which means smart parents have children that are smarter than average but less smart on average than their parents. Same thing for dumbs. The upshot of this is if Country A has an average IQ of 100 and Country B has an average IQ of 85, if A imports everyone from B with an IQ of over 115 all that will be accomplished in a few generations is to lower the average IQ of both countries.