Everyone has faced this question during life, but the scientific answer is not as widespread. Now, scientists give an answer to this riddle.
Chickens as a species have become chickens after a long and slow process of evolution. At one point, the same bird hen produced a follower, as a result of a mutation of DNA, has crossed the threshold that separates species “like chicken” to “real chicken”. More specifically, a proto-chicken produced a true hen. Because this resulted in real chicken egg, we can say that egg was first.
Another way we can answer this question is to ask which of the two was the first in evolutionary history. Again, the egg was first. Many of the modern avian egg – oblong shape and asymmetrical hard shell – were long before birds separate from dinosaurs about 150 million years ago. “Many of the features we see in the eggs of birds have evolved before birds from dinosaurs theropods,” says Daria Zelenitsky at the University of Calgary.
Another key moment in the history of avian eggs occurred before the dinosaurs 150 million theropods when part of the vertebrates with four limbs have evolved to produce amniotic eggs. Embryos from these eggs were surrounded by three membranes filled with fluid that provides food, protection and a way to breathe. The earliest amniotic egg yolk has large amounts, says James R. Stewart, a specialist in reproductive physiology at the University of East Tennessee. “This can be further seen in birds, crocodiles and snakes,” said the expert.
Like other placental mammals, humans have lost their egg somewhere along evolution, but present still a yolk sac (yolk) vestigial, attached to the embryo, which provides the necessary nutrients.