Today
- we have a very broad and abundant source of food (e.g. we get tomatoes in or out of season)
- most responsible parents start stimulating our children's intellect upon birth (some try before birth)
- we have added more knowledge over the last 50 yeas than in all of human history and made it readily available
So I think any degradation would be due to overly processed foods, too many drugs, and toxins from our high tech world getting into our food and air.
I would say the causes are more cultural. Since the eighties I have noticed the “dumb is kewl” trend. Add to that the sad state of dumbing down of public schools, and the school administration enforcing the “crab bucket” mentality.
We have added tremendous amounts of information. A significant portion of that is noise, not signal.
Not all information is knowledge, under the best circumstances, and much of what passes for information is incorrect.
What we are lacking is the ability as a culture to filter the information to gain knowledge, and the moral and philosophical basis to use the knowledge to derive wisdom.
The ability to throw more paint at a wall does not an artist make.