The vertebrate originated from the vertebrate and after that no vertebrate evolved to the vertebrate although billions of years have passed. Asked why?
--------
The question is – why? Who told you that ALL invertebrates are lower on the evolutionary ladder than vertebrates? Who put this heresy in your head? Why did you decide that bees and ants are better developed? Is it because you personally weigh more or because you can pollute nature faster than any other species? They are not worse than yours, just differently. This is another branch, not worse, not better, but simply another, neighboring one. How else to explain? If your neighbors don’t have a carpet on the wall, that doesn’t mean they’re idiots. You may be an idiot.
Insects, for example, evolved no less time than humans, and, from a biological point of view, developed very well. This is the age of insects, not mammals. It was the dinosaur era, for example. Insects develop very quickly, live in any environment, and the total biomass is much more than all vertebrates combined.
This is not to mention the "billions" of years of evolution, and the fact that the living nature in principle does not have the habit to accurately repeat what has already been done once, the maximum - the same function repeats in another material. Well, teach biology at the end of the day, at least take a school textbook.