Evolution is fascinating, but one question has baffled so many for a long time: which came first, the chicken or the egg? It is a simple question, no doubt, but also one of the most interesting. We all know that the chicken gives rise to the egg, but curious minds will want to know which came first at the beginning of time.
What makes the question so tricky is that a chicken is needed before an egg can be laid, but chickens come from eggs so we are left with a confusing cycle. This article’s essence is to unravel this very intriguing mystery, with all the thanks going to the discoveries made by evolutionary biologists.
The First Eggs
There is no part of the animal kingdom that you turn, and you will not see eggs – they are just everywhere. By definition, an egg is a vessel covered by a membrane in which an embryo can achieve growth and development until it can survive without help.
That said, we will shift focus to the kind of eggs from birds that we know today. These eggs were first seen with the coming of the earliest amniotes millions of years ago. Before these arrived, the animals had to depend on the water for their reproductive phases so they laid the eggs inside ponds or practically where there is water and this was to ensure that the eggs do not dry out at all as that will mean the end.
It was noticed that after some time, a new variant of egg started evolving, and this that three additional membranes inside it. These were called the amnion, chorion, and allantois. Every membrane had its specific function, but it was noted that the inclusion of these additional layers meant proper enclosure for the embryo. It can get practically everything that it needed.
The embryo could absorb stored food, reserve excess waste items, and even breathe without the need for staying inside water. There were also additional fluids inside the amnion and alongside the resilient shell, which offered additional protection.
Amniotic eggs were remarkable and they led to more openings for eggs to be laid on land and the additional membranes led to the creation of even bigger eggs. Scientists do not know precisely when this occurred because there are not very good fossils for amniotic eggs.
However, they surmise that the last joint ancestors of tetrapods and amniotes existed around 350 million years ago; some estimate it at 320 million years ago. All reptiles, mammals, and birds today all came from the first set of amniotes.
The First Chickens
The first chicken is believed to have resulted from a genetic mutation that happened in a zygote that came from proto-chickens. This implies that the mating of proto-chickens led to a combination of their DNA, which led to the formation of the first chicken.
Genetic mutations would later occur in that initial cell and these mutations were duplicated in all the cells of the chicken embryo as it developed and this was what led to the first true chicken.
Some will ask who the parents of this first true chicken were and that brings us to the red jungle fowl (Gallus gallus). The red jungle fowl is native to Southeast Asia and it is believed that human beings did domestication of this bird in Asia and later spread it all over the globe as the less wild ones and egg layers that we now call Gallus gallus domesticus.
Discoveries by archeologists have led us to believe that the red jungle fowl was first domesticated about 10,000 years ago even though some other studies suggest a much earlier time. There is also some proof that there might have been some hybridization along the line but the details are still sketchy.
The First Chicken Eggs
Some said that the chicken came first, which was based on the formation of the chicken eggshells. The shell of an egg is made up mainly of calcium carbonate. Hens can get the calcium needed for the production of eggshell from the foods they consume.
The formation of a shell needs the deposition of calcium carbonate crystals, but they will also need some particular proteins for this process to be complete. This protein is seen only in the ovary of a chicken, and this led some to say that the chicken must have come before the egg as the protein, which is known as ovocleidin-17, is a must for the formation of a chicken egg.
At the end of the day, it is apparent to us all that the eggs came before the chickens, but chicken eggs did not because you cannot have one without the other. If you are still confused, let us simplify it for you – the egg came first.