Which came first, the chicken or the egg?

The question of whether the chicken or the egg came first has been ceaselessly and exhaustively discussed across various sectors of society, from philosophy to paleontology, and even to the field of life sciences.

What is the relationship between chickens and birds? Chickens belong to the Animalia kingdom, Chordata phylum, Vertebrata subphylum, and Aves class. According to the ancient Greek philosopher Aristotle (384-322 BC), "It is impossible for there to be the first egg that produced a bird, because there must have been a bird capable of laying that first egg." According to Buddhist teachings, all things in the world are a result of cause and effect, without beginning or end, and there is no question of which came first. Christianity posits that "God" created birds, which then laid eggs. Philosophical thoughts on the matter are varied. As for causality, it remains a mystery.

In 2008, Canadian paleontologists announced that the egg came before the chicken. They discovered five eggshells in a nest made of piled-up sand, which was half a meter wide and weighed 50 kilograms. Through research on this nest and the eggshells, the Canadian scientists claimed that dinosaurs first built nests similar to those of birds and laid eggs similar to bird eggs. Then, dinosaurs evolved into birds (with chickens being a type of bird), meaning that eggs existed before chickens. Chickens evolved from these meat-eating dinosaurs that laid eggshells similar to those of chickens.

So, following the line of thought of biologists, why would dinosaurs lay bird eggs? We know that dinosaurs had two types of cells in their bodies: somatic cells, which make up the internal organs, brain, skin, etc., and reproductive cells, which are related to reproduction. The substance that determines our heredity in cells is DNA, which can mutate due to various factors such as physical factors like radiation and temperature, chemical carcinogens like benzene and coal tar, and biological factors like viruses. If these factors caused mutations in the DNA of reproductive cells, it would have a significant impact on the offspring, such as mutations in the DNA of dinosaur reproductive cells that led to the production of eggs similar to bird eggs. When this bird egg hatched, it might have possessed the physiological function of laying eggs. Therefore, the first bird must have come from the first bird egg.

Just as we come to the realization that it was the egg that came first, British scientists give us another perspective, arguing that the chicken came before the egg. In 2010, British scientists Dr. Foresight and Dr. Oldman, among other researchers, discovered that the formation of an egg depends on a protein found in the mother hen's ovary, called ovocleidin-17 (abbreviated as OC-17). OC-17 protein controls the synthesis of eggs, and without OC-17 protein, the outer part of the egg cannot crystallize to form the eggshell. In other words, OC-17 protein is a key factor in the formation of the eggshell. However, scientists also found that OC-17 protein can only be generated in the ovaries of birds. At this point, we might wonder, what is the reason for this? Just as the age-old mystery seems to be solved, it is overturned again?

At this point, someone might ask, what do we call the organism that laid the egg? Is it a bird or a dinosaur? This is the crux of the matter. If the first organism that laid a bird egg is called a dinosaur, not a bird, then it would be the egg that came first, followed by the chicken. If the organism that could lay bird eggs is called a bird, then it must be the chicken that came first, followed by the egg.

As is well known, biology has a certain classification system, a method used to categorize species of organisms. The modern biological classification system originates from Linnaeus's system, which classifies species based on shared physiological characteristics. Linnaeus divided the natural world into three kingdoms: plants, animals, and minerals, and under the kingdoms of animals and plants, he established four levels: class, order, genus, and species, thus establishing a hierarchical classification system. After Linnaeus, this system was gradually improved based on Darwin's principle of common ancestry. In recent years, molecular systematics has used bioinformatics methods to analyze genomic DNA, significantly altering many existing classifications.

Therefore, in my view, the first dinosaur that laid an egg similar to a bird's egg had physiological characteristics no different from other dinosaurs; it was just that the egg it laid underwent a certain degree of variation, similar to a bird's egg. According to biological classification, it should be considered a dinosaur. As for the OC-17 protein argument, dinosaurs also laid eggs, and the characteristics and shape of dinosaur eggs are similar to bird eggs. We can also speculate that the ovaries of dinosaurs might have produced OC-17 protein, but at that time, the dinosaur was still a dinosaur. Therefore, the egg came before the chicken.

So, what do you think? Which came first, the chicken or the egg?