Is the chicken born before the egg, or is the egg born before the chicken? This is a famous topic. It's famous because the question seems simple, but it's difficult to answer. Choosing either answer seems to lead to a paradoxical situation: if the chicken comes first, then where does this chicken come from? Since all chickens are hatched from eggs, where would the chicken come from without eggs? If we say that the egg comes first, then similarly, where does this egg come from? There must be chickens in order to lay this egg, and without chickens, where would the eggs come from? Here, the egg specifically refers to chicken eggs. If this definition is not given, then this question would have many different interpretations and answers.
If the chicken here specifically refers to chickens or other birds, and the egg is not limited to chicken eggs or bird eggs, but refers to all eggs, then it's obviously the egg that comes first. Because from the ancestors of birds, reptiles, began to reproduce by laying eggs, and the appearance of eggs is much earlier than the appearance of birds. If the chicken here specifically refers to chickens, and the egg refers to all bird eggs, then it's also obvious that the bird egg comes first, and then the chicken species appear. Because the earliest birds were egg-laying, and the chicken species later diverged from early bird species.
This question is only a difficult one to answer when it is stated as "Is the chicken born before the egg" or "Is the bird born before the bird egg". Because it's both a scientific question and a philosophical question. To answer it, we need to understand the principles of species formation and the dialectical relationship between quantitative change and qualitative change. Species formation is the core of biological evolution. A new species diverges from an old species through three stages: genetic mutation, natural selection, and reproductive isolation. Through genetic mutation and natural selection, different populations of the original species gradually diverge. This divergence is a process of quantitative change. Only when the divergence accumulates to a certain extent and reproductive isolation occurs, that is, when two populations cannot interbreed to produce viable offspring, will these two populations become two species, and the new species will be formed.
Most species formations require a long process. Compared with the process of species formation, the process from chicken to egg or from egg to chicken is very short. In this sense, chickens and eggs, or birds and bird eggs, almost appeared at the same time. If we must distinguish the order, then it depends on which stage the final mutation leading to species formation occurs: if it occurs in the stage of egg development into chicken, then it can be said that the egg comes first and the chicken comes later; if it occurs in the stage of chicken producing eggs, then it can be said that the chicken comes first and the egg comes later.