The first was an egg, from which, under the influence of a temperature change or a gene mutation, a chicken appeared in the aftermath of the chicken.
What laid the egg that hatched out as a chicken? Let's, just for argument's sake, say it was a quail that laid the egg. If it was a quail that laid the egg that hatched out into a chicken, there would have to millions upon millions of mutations to convert a quail inside quail egg into a chicken. Evolution theory doesn't allow for that.
Okay, what about a "bird" that was a near chicken, that laid the egg that hatched the chicken out. Well, that "bird" would have to be so extremely near to being a chicken that nobody could tell the difference, anyway.
For example. If a wood sculptor wanted to sculpt a chair out of a log, he starts with the log, and chips a piece of wood out of the log. Then he chips another, and another and another, etc., until the log is a chair. What about the last chip of wood? Was it a chair before he chipped out the last piece of wood? Or was it still a log? How about the previous chip of wood. Actually, where is the point in which the log actually becomes a chair. Right from the start, because you can sit on a log just like you can sit on a chair?
Jokers like Dawkins might suggest that this animal evolved into that. But the mutation "chip" that changes the final animal from the previous animal, is so tiny that you couldn't tell the difference between the two animals. Like begets like, and that is all that we see. We have no example or experience of an animal that has converted from a different animal by mutation "chip." Like begets like. That's all we have experience and example of.