what's lacking or in excess in our current environment that would cause a population-wide K2 deficiency? I've never heard of K2 :)
Well, people don't eat enough Vitamin K2. Vitamin K2 (MK-4) comes from the following sources:
Butter, Eggs, Marrow, Brains ...
K2 (MK-7) comes from these things: Natto, Aged Cheese, etc
The human body can convert K1 (Spinach, Kale etc) to K2, but not very efficiently.
Among many other things, the human body uses K2 to build enamel on teeth, strong jaws etc. It's also responsible from keeping bone healthy.
Hope that made you curious. PM me for a good link on K2