The question of who came first: "the chicken, or the egg?" is an age old paradox that finds its roots in the musings of ancient philosophers of old, Aristotle, Plato, Plutarch etc. who pondered upon such conundrums as they were evocative of the creation of life, of bird, and of the Universe. The question, which was originally postulated as a metaphysical or symbolic one in nature, alluding to the supposedly unsolvable case of a circular cause and consequence dilemma, has nonetheless found much weight in a literal sense today. Scientists, for instance, are interested to know which came first because it will undoubtedly shed much light on the evolutionary history of chickens, or indeed, of birds in general, while regular folk like us on the ground want to know simply because it is interesting and would (probably) put the worn out conundrum to rest once and for all!
Thankfully for those of us who are interested, conventional scientific understanding of the evolution of animals may have answered that question for us once and for all. Based on our current understanding of the world through science, all living beings came to be through the process of evolution and natural selection. Evolution, or the gradual adaptation of animals that results in the manifestation of unique new, and distinct forms of animals, is largely considered to be a cross-generational process. What this means is that no species can exist spontaneously and no animal evolves into another species during its lifetime. Instead, the genetic markers for any given species are passed on to the offspring of that animal by its parents and with each generation, grows to be more and more refined and defined until the resulting offspring several generations hence is considered to be almost entirely genetically distinct from the birds that bore its forefathers. This point of differentiation is also known as the "threshold" upon which a new species is born.
The domesticated fowl, or chicken as it is known, is not a naturally occurring species. Rather, it is a bird that is thought to have been "created" by humans over at least 5000 years through the process of artificial selection. Artificial selection is the breeding of various birds with the sole purpose of refining or bringing out specific genetic markers and traits.The ancestry of the domesticated chicken is still one that is commonly debated but many sources concur that at least one of the chicken's ancestors was the red jungle-fowl, a tropical pheasant that still exists in the wild across Asia, and the grey jungle-fowl which is endemic to India. The chicken, as the resulting offspring of the red jungle-fowl, and the grey jungle-fowl, is therefore to be regarded as a very specialized hybrid. Therefore, this stands to reason that the "chicken" in turn did not come to be until a "threshold" was crossed that differentiates the "chicken" from its ancestors. The first bird that was said to have crossed this "threshold" and come to be regarded as the very "first chicken" had to have hatched from an egg, the "first chicken egg", while the parents of said offspring, by definition, occupied a position that was on the other side of the "threshold" and were therefore not considered to be a chicken per say. For many scientists, this seems to have settled the argument once and for all: that the egg came first, before the chicken.
Evolutionary philosophers, however, have postulated that the genetic markers that eventually resulted in the emergence of the domestic chicken species had to have always existed in some way in the ancestor birds and theoretically could be traced back to before the evolution of birds themselves which, for them, seems to indicate that on a cellular level, it was arguably the "chicken" that came first, before birds, indeed, before all egg-laying animals and so in some way the conundrum continues to those who find currency with this latter explanation. Another thing that the chicken and the egg conundrum can show however, is is also how important and significant these birds really are to the development of human culture and society. Of all the animals in the world, it is often argued that the chicken is the most influential to humans whose own evolutionary history is the most closely tied to our own. Almost every single culture in the world makes allusion to chickens, whether as food, totems, or as religious and spiritual symbols and chickens commonly serve various purposes in the day-to-day functions of ancient societies. In the modern world, chickens are one of the most common and widespread of all the domesticated animals, including pets. There are an estimated 26 billion chickens currently living in the world which makes them the most abundant species of bird known to man.
Despite having gone through thousands of years of domestication, chickens are considered by many to be highly social birds that quickly establish flock hierarchies, or pecking orders, that are similar to those employed by their counterparts in the wild. Unlike many other species of birds whose eggs and chicks fall under the responsibility of one, or both, the biological parents, many chickens take a communal approach to egg hatching and chick rearing with mothers often choosing to lay in similar locations, sometimes even in the same nest. Roosters are commonly the dominant chicken in any given flock and are known to call loudly to gather the flock when food is found. Due to the escape of domesticated chickens and free-range chicken rearing in the outskirts of Asia, the wild counterparts of the domestic chicken such as the red jungle-fowl, green jungle-fowl, and grey jungle-fowl species are considered to be threatened and susceptible to extinction due to hybridization with domesticated birds that results in the dilution of the wild gene and its resulting traits such as longer wings, lighter more stream-lined bodies (meaning these birds are capable of long and sustained flight) that are more suited for survival in the wild.