"Due to our lack of large claws or 35mph+ sprinting ability without technology we die out from B12 deficiency."

Earthworms are an excellent source of B12. No spears needed...

https://kb.osu.edu/dspace/bitstream/1811/22250/1/V074N6_359

Moreover, cats eat a lot of insects. If I am not mistaken cats are even worse off in their need for fatty acids and proteins than we are because they have a more specialized diet than us. If you watch your cat hunt for small animals and insects, you might learn a lot about how to get by without any tools.

:-)

And non-Western ppls eat bugs happily for wonderful treats they are. Bugs can be raised, or of course if human population goes way down like it should, there will be plenty free-range.

A photo helps to visualize the tasty treats available on the street here in SE Asia.