Egg

Yolks knew they were about color since people named them--the Old English word geolca literally meant "the yellow part". They had a successful career as a binding medium in paint known as egg tempera which was popular in medieval Europe. Later on Velazquez would paint Old Woman Frying Eggs in oils, which don't hold their color as well as tempera and will darken and yellow, which coincidentally will make the eggs in the painting score higher when using a DSM YolkFan™ which has a calibrated set of yolk colors building on decades of research on "what color is that yolk" (see for example Ashton and Fletcher's Development and Use of Color Standards for Egg Yolks, 1962), aligning them with European consumer preferences where people like darker egg yolks than Americans. Yolk color is so important in egg sales that there are now dietary supplements featuring particular carotenoid ratios for hens which result in specific colors, some of which have no bearing on nutritional content. Without supplementation yolk color indicates how many foraged greens hens ate because animals can't synthesize carotenoids, so yolks were historically less vibrant in the winter. (Speaking of color and consumer preferences, the US Department of Agriculture advises that eggs sell better when they are all the same shell color in one box. Too bad.) Some eggs have two or even three yolks. Whoops. Some have none. That's pretty common for a hen's first egg. Those used to be called cock's eggs because people thought roosters were responsible for laying eggs without yolks. Whoops.

The USDA publishes standards for grading eggs into AA, A, and B grades, which fits in its purview thanks to the Agricultural Marketing Act of 1946. One of the measures for these standards is the Haugh unit which is calculated based on the weight of the egg and, after cracking it, the height of the thickest part of the egg white near the yolk. Thicker whites means higher quality eggs, see Haugh 1937 (now impossible to find on the internet) or the earlier and more available The Albumen Index as a Physical Measurement of Observed Egg Quality from 1935 by Heiman and Carver, which includes such scientific statements such as "For the breaking operation, the eggs were picked up with the right hand with the large end of the egg to the left". The scientific study of egg whites also led to the first imaging of an enzyme, carried out in 1965 on lysozyme taken from egg whites. Lysozyme is also found in mucus and its name is basically "cutter" because it rips apart bacteria and is useful in natural immunity. The study of immunology has benefitted from eggs greatly, with the interferon discovered in 1957 by studying viruses in the chorio-allantoic membrane of 10-11 day old chick embryos (an immunosuppressed environment). The study of viruses in eggs goes back to 1931 and resulted in the development and production of the first influenza vaccines. In the collection of Jonas Salk's research materials housed at the Special Collections & Archives, UC San Diego you'll find a box of spiral notebooks, Box 542, in which there is subset labeled, you guessed it: eggs.

Before people were studying eggs for immunity they were learning other things about protection: how to get eggs from one place to another without breaking. The original egg box was made by interleaved slats of cardboard, like strings in a tennis racket dividing up little squares for the eggs to sit in a cushioned wooden box. Once egg distributors could buy protection it became quite the racket itself, and carton-makers sought protection themselves through patents, with Morris Koppelman filing over two dozen and Joseph Coyle a dozen and a half.

The eggs, though, always had their own protection. Shells made out of calcium carbonate form by crystalline deposition on a membrane which you can see if you gently crack and peel the shell off. The yolk is enclosed in its own membrane so that it doesn't get all mixed up with the whites and is suspended inside of the shell by those white strings you'll see on the yolk of a cracked egg called chalaza. Suspending something inside a protective shell with elastic strings is frequently used to isolate the interior from the outside like in atomic clocks and quantum computers. It seems the ability of a system to process information internal to itself requires some level of decoupling from environmental noise, as anyone who has tried to write with a leaf blower roaring outside their window can attest. In that isolation, the baby chick develops.