Short answers, pulled from the story.
Humans have grown and selectively bred onions for at least 7,000 years. Domestication is believed to have taken place in West or Central Asia, though ancient records of onion use span both eastern and western Asia.
Cutting an onion damages its cells and releases enzymes called alliinases, which break down amino acid sulfoxides to produce sulfenic acids. A specific enzyme, lacrimatory factor synthase (LFS), converts one of these acids into syn-propanethial-S-oxide, a volatile gas that activates sensory neurons in the eyes and triggers tear production.
Sunions are the first commercially available LFS-silenced onions, released by Bayer in early 2018. They were developed over 30 years of cross-breeding, without genetic modification, to prevent synthesis of the lachrymatory factor that causes eye irritation.
The oldest known recipes in the world are the Yale culinary tablets, ancient Mesopotamian recipes pressed into clay in cuneiform script and dating from around 2000 BC. They record dishes using onions and other Allium species.
Shallots have the highest polyphenol content of the common onion varieties, carrying six times the amount found in Vidalia onions. Yellow onions have the highest total flavonoid content among the main colour varieties, at a level 11 times higher than white onions.
Ancient Egyptians revered the onion bulb, viewing its spherical shape and concentric rings as symbols of eternal life. Onions were placed in burials; onion traces were found in the eye sockets of Ramesses IV.