In order for an egg to appear, it must be laid by a chicken,but the chicken is known to come from the egg. So what came first? This is a well-known logical paradox that was discussed by the philosophers of ancient Greece thousands of years ago. True, initially the question concerned birds in general, and not chicken. Opinions on this score varied. For example, Aristotle believed that there was nothing primary at all, since the bird and the egg appeared at the same time. Currently, many people believe that there is no answer to this popular question, but this is not the case. Biologists, paleontologists and evolutionists know the exact answer. However, it depends on what kind of egg will be discussed.
- 1 What is an egg
- 2 What were the very first eggs
- 3 How birds appeared
- 4 Did the chicken come before the egg?
What is an egg
To answer which came first - an egg orchicken, you need to figure out what an egg is. In fact, it is just an egg, that is, a female germ cell, from which, after fertilization or as a result of parthenogenesis (asexual reproduction), a new organism develops. According to scientists, an egg with a hard outer shell that can be laid on land is an important step in the evolution of vertebrates.
Before the appearance of the eggs that contain the embryo,nutritious yolk and hard shell, vertebrates had to rely on bodies of water in which to lay their eggs to reproduce. Yes, caviar is, in fact, the same eggs, but without a hard shell. Most amphibians to this day are faced with the need to provide a certain amount of humidity in order to get offspring.
What were the first eggs?
Considering all of the above, the egg appeared earlierchickens, and in general before all birds on Earth. According to the University of Texas at the Austin Biodiversity Center, the oldest hard-shell fossilized eggs are 325 million years old. Birds appeared much later. As reported in a study published in the journal Current Biology, this happened between 165 and 150 million years ago.
True, according to scientists, the first eggs did not havesuch a hard shell as it is now. They had hard skin as a shell, making them softer. For this reason, such eggs rarely become fossils, according to a study published in the journal Nature.
Another study of 200 million eggsyears showed that it had a very thin shell, the thickness of which did not exceed 100 microns, or 0.1 millimeter. Approximately the same thickness has a human hair. However, according to scientists, they were already as hard as porcelain. That is, this is the earliest example of eggs identical to modern ones. True, they are also very poorly preserved to this day.
How birds appeared
To summarize all of the above, Aristotlewas wrong. The egg appeared much earlier than the bird. Most likely, the caviar that the first amphibians laid, over time, began to acquire an increasingly hard shell, which eventually turned into a shell. As a result, eggs appeared before birds, as we found out, by more than 150 million years.
Between 325 million years ago and 150Millions of years ago there were many vertebrates that laid eggs, but the most famous of them are the dinosaurs. As we said earlier, birds are also dinosaurs, or rather, they became an offshoot of theropods, bipedal predatory dinosaurs.
About transitional species between dinosaurs and birds, wehave been told many times before. One of them is a bird with the head of a tyrannosaurus - Cratonavis zhui. Accordingly, when birds arose, they were already laying eggs, like all other dinosaurs.
Did the chicken come before the egg?
It would seem that the question can be closed - eggappeared before birds. But our question is about the chicken, not all the birds. And here you can argue about what is primary and what is secondary. According to scientists, the Kura (Gallus gallus domesticus) most likely originated from red wild birds (Gallus gallus), which appeared about 50 million years ago.
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As reported in a 2022 studyit is said that people domesticated this bird between 1650 and 1250 BC. At some final stage of domestication, the ancestor of modern chickens laid an egg. This egg contained an embryo that contained many genetic differences from the wild ancestor, but at the same time, the egg itself was not a chicken. When the chick hatched and grew up, he laid the first real chicken egg. So the chicken came before the egg.