History of Eggs as Food.
People have been eating eggs since there first started to be people, about six million years ago. Eggs have a lot of protein in them, and they don't fight back - you can get them just by climbing to where the nest is and picking them up.
By about 7000 BC, people in China and India were keeping chickens and eating their eggs, so they didn't have to go hunting for wild bird eggs anymore.
Chicken eggs didn't reach West Asia, Egypt, or Europe until about 800 BC, or even later, and people in southern Africa didn't start to eat chicken eggs until about 500 AD. Before that, Europeans and West Asians kept ducks and geese for their eggs. About 300 BC, chicken farmers in both Egypt and China worked out ways to incubate chicken eggs in warm clay ovens, so that they didn't need to have hens sit on their eggs to hatch them, and instead the hens could lay more eggs. This factory system made chicken eggs cheaper, and more people began to eat them.