<p>I suspect there may be truth to it, but I don’t think it has to do with evolution or anything like that. If there is an increase in IQ, I suspect it is because for the most part people are in general have a diet higher in protein than our grandparents did and for the most part we are better nourished (before someone makes the point about obesity, processed foods, chemicals in the diet, etc, and how our grandparents ate 'non processed foods, I will conceded that, but I am talking protein intake and calories available). In our grandparents day, a lot of people were not living a middle class lifestyle, many of them often had a struggle to put food on the table, to consistently have enough to eat, and that was true whether you were a farmer or a laborer or working in a factory, it was simply a lot more of a struggle to live. One thing I am certain of, our diet in our generation has a lot more protein in it, and that makes a difference with brain development and such, plus we also probably have had better intake of vitamins and such (when was the last time you heard of a kid in the US with Ricketts? ). All of that I suspect has led to the brains being better developed on average, so there could be truth to that. </p>
<p>Likewise, modern medicine also has a role, a lot of the diseases and such that are treatable today could have impact on the brain, so that is another factor.</p>
<p>I don’t think the brain’s potential has changed, I think it could be we achieve more of potential of our brains on average because of better diet and medical care. </p>
<p>The factor that works the other way is the nature of IQ tests, despite all the hemming and hawing about how bad education is today, in our grandparents day a lot of people never even finished high school, and a lot of people were poorly educated. When my dad was in WWII (he would be 90 if he was with us today), he was shocked how many guys he saw in the army who were either illiterate or barely literate, and there were people, especially from rural areas, who really shocked him at how little education they had had, compared to him, a kid from the Bronx who never thought he was particularly well educated. Despite claims to the contrary, most iq tests have biases that favor more educated people, so it may be hard to compare because of that.</p>