It’s also possible that they were eating a lot more high zinc foods in cold climates (think organ meats and seafood like mussels). Getting too much zinc is as b

It’s also possible that they were eating a lot more high zinc foods in cold climates (think organ meats and seafood like mussels). Getting too much zinc is as bad as getting too little so genetic adaptation would favor slower intestinal zinc transport and higher mitochondrial, zinc export which is what the SLC30A9 gene does. So now, those of us who carry this variant and are eating a lower zinc diet get way too deficient to easily.