What came first then? The dinosaur or the egg?

Answer

Well, Aron, of course it wasn’t that easy. It is not the case that, 200 million years ago, one sunny morning suddenly an egg lay in the savannah. Or that a female dinosaur suddenly felt the need to lay an egg. Just like the chickens, the dinosaurs also had predecessors: the first four-legged land animals, and they in turn descend from fish-like ancestors that lived in the water. It all happened very gradually, and it took a very long time. The oldest traces of living beings date from 3.5 billion years ago, which is an unimaginably long time. If instead of those 3.5 billion years all evolution had taken only one year, from January 1 to December 31, there would only be single-celled creatures until October. During the month of October, more complex living creatures gradually emerge, including primitive fish that already have a kind of backbone. From mid-November you will gradually also find life on land, and from December 10 until close to Christmas is the flowering time of the dinosaurs. Humanoids only appear on New Year’s Eve in the afternoon, modern humans at a quarter to midnight…
If I now say: the egg came first because those primitive four-legged friends also laid eggs, then I already know what you are going to ask. So let’s go all the way back to those very first primitive living creatures of the first 3 billion years. They didn’t look like a chicken or a dinosaur at all, they looked a bit more like an egg, but they really weren’t eggs either. An important moment in evolution, which has to do with your question, is the emergence of a system of reproduction with two partners. The oldest single-celled creatures reproduced by dividing, and there are still many single-celled creatures that reproduce in this way today. But an egg implies a father and a mother – so you have to look for the most ancient ancestors of eggs among the very first creatures that reproduced that way. Unfortunately, you don’t find that kind of information about reproductive systems in the oldest fossils that are our witnesses to how evolution happened. So it remains, I’m afraid, a question to think about, a question that can allow us all to learn a great deal if we think about it, but a question with no definitive answer.