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

They need tummy time to strengthen they’re back and so they’re not lying down so much. A v shaped cushion is to support them sitting is better for them than a seat.