I think it facile to speak of "intelligence" - what we have are cognitive functions that group together into "intelligences."
Hence the curious and poorly understood mechanism by which some people who are deemed "autistic" have extraordinary, albeit fairly discrete gifts - photographic memory, or the ability to play a song by ear.
We used to think adults didn't generate new neurons. They do.
We used to think "junk DNA" served no genetic purpose.
Lamarck may not be quite vindicated, but more and more we see that 'epigenetic' factors influence heritable traits.
Another way to look at evolution is to see the evolution of adaptability *per se*.
Yes, you can increase your cognitive functions, whether you're starting a job as a tax driver in London, or playing the coolest new video game, or learning how to play chess.
As the research paper writings expert claims, these new skills represent changes to brain wiring, and possible new neurons.
A healthy mind works best in a healthy body but if you want to increase your ability to learn and remember - spend more time expending mental effort trying to learn and remember!
It also doesn't hurt to ask your physician about vitamin supplements.
I suspect a lack of vitamin D in the winter contributes not just to depressed mood in some but to diminished cognitive function.