How old are your cells? By measuring the new Carbon 14 atoms in cells we have found your surface tongue cells and intestinal lining to be 5 days old. Those cells are replaced and regenerated fastest. Your hippocampus cells are no more than 30. Your heart cells are up to 16.9 years old.
But your cerebral cortex and glial cells are as old as you are.
So if you don't drink alcohol like me I will grow proportionately smarter than all you drinkers each passing year without my growing smarter at all.
WHAT?
All those extra cortex convolutions found in learned people are not new neurons?
Hmmm live and learn, die and forget it all.
At least were all young at heart.