The change from adult to child is not an evolutionary change.
Please understand this. Back to square one. (We need at least a single piece of the puzzle—just one will do for starters.)
Fossils from 3 million years ago suggest discrete species, separated by immense gaps in genetic information. If evolution were true, these gaps would not be there.
If you even understood the first thing about evolution you would understand that.
Fossils from 3 million years ago suggest discrete species, just one that HAPPENS to look like what you would expect a human to look like that had only half as much distance from a common ancestor as a human.
If the evolutionary model were an accurate predictor of reality, then that is exactly what you would expect from fossils 3 million years ago. And there they are.
Just as when they looked for a shoreline around the time tetrapods were evolving, darned if they didn't find a “transitional” that looked like half a fish and half a salamander.