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“We have given you, O Adam, no visage proper to yourself, nor endowment properly your own, in order that whatever place, whatever form, whatever gifts you may, with premeditation, select, these same you may have and possess through your own judgement and decision […] We have made you a creature neither of heaven nor of earth, neither mortal nor immortal as the free and proud shaper of your own being, fashion yourself in the form you may prefer.”
Oration on the Dignity of Man – Giovanni Pico della Mirandola

Hatching from eggs

published on 9.04.2020

On Easter Monday, it is a tradition that the godparents give a cake (“mona”) to their godchildren. There are many different varieties of cakes, such as roscón, sponge cake, chocolate cake… but they all have eggs on top. Why do we incorporate eggs into this celebration? There are two hypotheses: between the ancient Egyptians and the Sumerians, the egg was associated with the life cycle and the rebirth of life around the spring equinox. This symbolism could have influenced the first Christian communities in Mesopotamia, and from there it could be transmitted to the Greek Orthodox community, and finally to Catholics and Protestants. A second hypothesis states that this tradition was born in the Middle Ages as a consequence of the fast imposed during Lent, according to which neither meat nor eggs could be consumed, and therefore, since the chickens did not stop laying, the eggs accumulated and they had to be consumed at Easter before they spoiled.
The egg is a great evolutionary invention as it confers a stable environment to the embryo so that it can develop until it is able to fend for itself. The amniote egg, with its insulating membranes, allowed reproduction outside the water, and therefore, was fundamental for the colonization of the terrestrial environment, some 330 million years ago. From then on dinosaurs, reptiles, birds and mammals appeared.
There is a great diversity of shapes, sizes and colors of eggs. The most popular for us are the bird’s eggs. The ostrich lays the largest eggs in world and the bee hummingbird the smallest. But when we compare the size of the eggs with the size of the birds we see that the relationship is not constant. The larger the bird, the smaller -proportionally- its egg, and conversely, the smaller the bird, the larger -proportionally- its egg. Thus, there are certain limitations in both the maximum and the minimum size of the eggs.
Although it is surprising, mammals we also reproduce by “eggs”. The female oocyte with its cover called the pellucid zone is a miniature egg. When fertilized, it forms the morula first and between the 5th and 6th day of gestation it forms the blastocyst and implants in the female uterus. There, it will form the umbilical cord from structures that in reptiles give rise to the yolk of the egg. It is, therefore, an “egg connected” to the mother. Finally, after pregnancy, labor occurs. In one out of every 80,000 cases, the child is born inside the whole amniotic sac and there is an opportunity to see to what extent humans continue to be linked to eggs for reproduction.

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