My take is a bit more akin to real life.
Babies 0-2 (at which point they begin walking and using pullups)
Toddlers 2-5 (at which point they begin talking and going to first grade here)
Child 5-9 (enters grade school)
Preteen 10-12 (yes, I believe we need this stage, otherwise, include this range in Child)
Teen 13-18 (at 18 are legal adults)
Young Adults 18-25 (the human brain isn't fully mature until around age 25, according to scientists)
Adults 25-72 (at which point they may retire)
Elders 72+ (retired)