It is one of the fundamental questions of philosophy. What came first? The hen that laid the first egg or the egg that hatched the first hen? Now, not only since Richard David Precht did we know that philosophy is a discipline that thinks a lot and says a lot, but not one that provides concrete solutions to essential questions. The chicken-egg answer is actually quite simple.
The egg came first, and with good reason. 400 million years ago, the first vertebrates conquered the land. Like today’s amphibians, they laid their offspring as spawn in ponds and riparian regions. The larvae therefore had to swim before they could follow their parents. This is impractical for pure country dwellers.
The solution was the development of the egg – protected on the outside by a solid membrane, on the inside a complex “habitat” for the embryos, which ensures breathing and nourishment. With this construct, the vertebrates were independent of water and were able to conquer the entire supercontinent Pangea.
Early mammals also laid eggs
Over the course of time, dinosaurs and early mammals also used this recipe for success in reproduction. The egg itself continued to develop. A very early evidence are 215 million year old fossils of Mussaurus embryos. The offspring of the small herbivores were found curled up, surrounded by a white veil. Researchers assume that these are traces of white, leathery egg shells, as we know them from turtles today.
The Pacific makes way for the next supercontinent
A new supercontinent could emerge within the next 200 to 300 million years. For this, the oldest ocean on earth, the Pacific Ocean, has to give way. The process is already underway.
There are 70 million year old finds of ovirapto eggs from China that are much more chicken-like. The feathered dinosaur is vaguely reminiscent of today’s ostriches. The shell of his eggs was firm and colored blue-green, with small brown speckles on it. This coloration probably served as a protection against predators and is an indication that oviraptors bred in open nests. The small dinosaurs then hatched from the eggs after three to six months.
Laying eggs was a disadvantage at some point
In the slipstream of the dinosaurs, the early mammals in particular developed the ability to carry embryos in their bodies for longer and give birth alive. What sounds like a contradiction was a smooth transition. Both variants of reproduction already existed 66 million years ago. When the asteroid hit the earth, the dinosaurs were not only doomed by volcanoes, tidal waves and a darkened sun, but also by laying their eggs. The baby dinosaurs took several months to hatch. For comparison: With today’s birds it is a few weeks, sometimes even just days.
It also took too long to grow from a small dino to a terrible lizard. Small mammals, which fed on very different things, sometimes lived in caves and also provided their offspring with milk, suddenly had a clear advantage. Despite this small setback in egg evolution, both birth variants still coexist today. Depending on the environmental conditions, the advantages of one strategy or the other outweigh the disadvantages.
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