Evolution and history of eggs

The egg is one of two reproductive cells (the other being the sperm cell), which when fertilized accomodates two gene sets, divides, and differentiates into the embryonic organism. It provides food for the inital stages of growth. Eggs are nutritious because they are designed to be food; they are designed to support new creatures until they are able to fend for themselves.

History dates back to the development of sexual reproduction in multiple-cell organisms. Around 300 million years ago, land dwelling reptiles developed self-contained eggs with shells that prevented fatal moisture loss and provided enough nutrients to support embryonic development into a fully formed animal. About 100 million years later, birds came along. Bird eggs developed a mineralized shell and antimicrobial defenses. These refinements made bird eggs a perfect human food. The egg contains a sizeable and balanced portion of animal nutrients, it is pre-packaged, and it stores well with little or no effort.

The genus Gallus, to which the chicken belongs, came along around 8 million years ago; but the chicken did not become domesticated until around 7500 BCE. From then, the eggs of different fowl made their way through many cultures and peoples. Chickens became prized because of their egg-laying behavior. Some fowl will only lay a certain number of eggs at a time, no matter what happens to the eggs. Others, including chickens, will lay eggs until they accumulate a certain number in their nest. If one of the eggs is taken away, the chicken will lay another to replace it and may do so indefinitely. Humans became the unrelenting predator who bound chickens to lay eggs day after day.

Bird eggs have been cooked probably since the discovery of fire. Salting and pickling eggs were performed by the Ancient. By the time of the Romans, many different recipes and uses were found for eggs. By medieval times, the French had mastered omelets. Yolk-based sauces and egg-white foams developed after the Renaissance.

Between 1850 and 1900, the chicken underwent an evolutionary change. The West was introduced to the Cochin, a Chinese breed of chicken, and a "hen fever" exploded. Hundreds of new breeds were developed. Breeds became prized for their meat or their egg-laying abilities. Today, most of the genetic diversity generated has disappeared. In the US, most chickens today are the product of four purebred grandparents.

The 20th century brought changes in industrialization and mass production. Today, most of the eggs come from egg factories, some of which house up to 1 million egg-laying hens. Most hens live in a cage-system which standarizes diet and social development; and streamlines egg collection, washing, and packaging. Hens in the US lay an average of 250 eggs a year, and suffer less than 5% mortality rate as opposed to free-range hens in the previous century, which laid around 100 eggs a year and suffered 40% mortality rate. The differences are attributed to improved housing (less exposure to the elements, disease, pecking orders, and predators), and more equitatable feeding. Furthermore, mass production exploded as refrigeration made fresh eggs readily and cheaply available. In many areas, eggs are available to the consumer within a day of it being laid by the hen.

Concerns have been raised about making chickens into biological machines. "Free-range," "organically-fed," and other specialty eggs have become available. While there is a benefit to their availability, people pay a hefty price for their concern, as much as 3x more. Even so, there are no clear guidelines as to what those labels mean. "Free range" in some cases only means a larger cage. Switzerland is the only country that requires that all hens have free access to the outdoors.