Quite the contrary, the world is far smarter than it ever has been, and it continues to get smarter every year.
Take for instance the world's second-largest country, India, in just the last 10 years literacy rates have jumped by double-digits in many states:
These numbers in India are going to continue to grow at a fast rate because young people are widely educated in the country, while the elderly -- especially in destitute areas -- represent a larger share of the illiterate. As destitute areas become less poor and as more elderly die and are replaced by a literate generation, literacy rates will reach a plateau likely higher than 90% throughout most of the country. Considering that in 1950, the literacy rate in india was
below 20%, this is staggering growth within a single person's lifetime.
If you look at the world literacy rate, in 1980, it was at 56%, by 2010 it was at 82% and today, it's likely around 85%
Also, it's insulting and completely wrong to suggest that if you follow some religious belief that makes you
less smart. Maybe if you're comparing a very small subset of the population, say, a Harvard educated biologist vs. a West Virginia high-school dropout evangelical, but worldwide, literacy has often accompanied the spread of the worlds largest religions. The two largest religions in the world Christianity and Islam, while certainly having a checkered past (and in some cases present), have widely advocated literacy as the primary means to engage with the religion... Reading the religious texts. People who can't read in any language will have a far more difficult time engaging in any "learned" activity, whether its science, math, philosophy, or anything else, and so you typically see a positive relationship between the spread of religion, the spread of literacy, and then the spread of other higher sciences.
Literacy is just one metric. It's likely the strongest metric, but still only one. That said, you'll see similar growth in most topics world wide decade over decade. Some years may see a regression, for instance, I'd imagine the recession in North America and Europe triggered a regression in rates of higher learning, but over the course of a decade, those will even out and likely rebound... And if we're talking world wide, then during the American recession, there was a surge of specialized learning in previously 3rd-world countries that were preparing employees for positions that companies were now competing on price for. So even if Europe or the United States saw slower growth in areas of higher learning in the late 2000s, that slack would be picked up in countries like India, China, Brazil, Nigeria, Ethiopia, and other developing economies with large populations.