Short answers, pulled from the story.
Archaeologists have found evidence of humans making cereal flour over 32,000 years ago. Wheat flour specifically has been traced back to at least 6000 BC, and a Natufian hunter-gatherer site called Shubayqa 1 in northwest Jordan, more than 14,000 years old, yielded evidence of bread making.
Bleached flour has been banned in Europe, Australia, and New Zealand because of concerns about the chemical agents used to whiten it and alter gluten development. In the United Kingdom, all bleaching and maturing agents, with the possible exception of ascorbic acid, are banned. The United States still permits bleached flour, where it is commonly treated with benzoyl peroxide or chlorine gas.
Bread flour contains 11.5-13.5% protein, which traps carbon dioxide from yeast fermentation and creates a chewy, well-risen loaf. Cake flour contains only 6-7% protein, producing minimal gluten development so the cake crumbles easily.
Flour dust suspended in air is explosive, as any finely powdered flammable substance becomes when mixed with air. The Tradeston Flour Mills in Glasgow exploded in 1872, killing eighteen people, and the Washburn "A" Mill in Minneapolis exploded in 1878, killing 22 people.
The fatty acids in the grain's germ oxidize when exposed to air, causing flour to go rancid within six to nine months. That shelf life was too short for industrial distribution networks of the late 19th century. Because vitamins and micronutrients were largely unknown at the time, removing the germ entirely was the practical solution.
Self-raising flour was invented by Henry Jones and patented in 1845. It comes pre-mixed with chemical leavening agents distributed evenly through the flour, ensuring a consistent rise in sponge cakes, scones, and muffins.