In the U.S., no consumer food product besides baby food is required by the FDA to state an expiration or best by date. Even in Canada, which has more stringent regulations on expiration than much of the Commonwealth, the CFIA only requires an expiry on foods which are primarily used for nutritional purposes which are known to lose their effect with age like meal replacements, supplements and prescribed diets. The date is only present on normal consumer foods by the manufacturers choice to co-ordinate stocking dates and to help shoppers.
Oh... right.
Most of the chemicals we use daily and rely on for manufacturing have only been synthesized in the last few decades, of course it's all going to be discovered to be awful for us. Early cans were made of raw tin or scrap aluminum, which meant they were impossible to apply sealants to and couldn't be sterilized properly, so anyone alive between 1800 and the early 1900's had a good chance of dying of botulism or salmonella. It's been this way ever since we began producing utensils - I can't imagine sharp rocks were the most sterile thing in the world to cut meat with.
