Eli5: why do babies sit with perfect posture when they learn to sit, but the older you get, the worse it gets?

Question

Babies sit straight up naturally. But the rest of us have to put effort in to having good posture, why?

In: 1304

Answer 1

Yet some “fitness professionals” use babies as example and emphasize on the fact we should squat and sit like them while completely ignoring the variables of muscle tone ,body proportions and weight, bone origins and insertions, center of gravity, genetics, etc.