I am bothered by the type of explanation exemplified by the NY Times article Why So Blue?, which purports to answer the question “Why do ‘Martha Stewart’ chickens produce blue and green eggs?”, “Martha Stewart chickens” are the Arucana breed she favors. Why does she favor them? Not mentioned.
It says that the breed produces “a pigment called oocyanin, a byproduct of bile production,” which apparently permeates the shell. The more usual mottled or brown colors apparently just rub off on the way down the oviduct. The normal stuff is from the breakdown of red blood cells. Hmm. Yuck?
This is not an explanation. It merely says the eggs are blue because they have a blue pigment, a statement that is not spectacularly explanatory. If I saw a blue egg, I would know it already. It just puts a meaningless language tag (oocyanin) on the pigment. You might as well say those chickens have a blue-producing property. It explains nothing.
I’m obviously not searching for something like “It was willed by God / Allah / &your_personal_deity.” Then I’d want to know why she or he willed it, and the answer to goes into the dead end of deities being ineffable.
I guess I’m looking for something like the following paragraph. I know we (probably?) can’t do this yet, but at least a nod in its direction would be nice.
Arucanas have key genome differences from other chicken breeds that define them as Arucanas; list them, if its' not too boring. Those key differences were produced by selective breeding or environmental pressure or random genetic drift; specify how much of each was involved and what it consisted of if appropriate. Those key differences cause oocyanin production because (a) the organization of the genome is such that having this [specify] key difference must imply oocyanin production – the two are coupled. Or (b) there’s no connection to the key differences, they just happened at the same time by chance. Specify one of (a) or (b). The oocyanin produced gets into the eggshells by such-and-such a process.
That would tell me why the dang eggs are blue.
Explaining why the sky is blue is a whole lot simpler.