> Nearly a year of "full time" work at 40hrs/week went into this
Sorry, I think you may be mistaken? From the section you quote, it looks like it's about 370 hours, or 9 weeks of full time effort. That's still a lot, but certainly not nearly a year.
I also don't think it rules out it being something for a child. It's not so rare to do big projects for you kids even today, over many evenings and weekends. And when you don't have any books to read or screens to watch...
You uh, missed a decimal point there. A year at 40 hours/week would be 2000 hours, not 200. The quote "unless the sculpture was created slowly at odd moments over several months" seems accurate in light of that, but rather odd: why wouldn't it be created slowly at odd moments over several months, or even years? Was prehistoric man lacking in free time? The article eventually continues: "why would a community living on the edge of subsistence, whose primary concerns were finding food, keeping that fire going, protecting children from predators, allow someone to spend so much time away from those tasks?" Keeping a fire going or protecting from predators are tasks with rather a lot of down time. I can easily imagine a person doing either of those while also whittling on a piece of bone. It's also just ridiculous to assume that subsistence living meant being constantly on the verge of starvation. Sometimes times were bad, and many people died. Then later, times were good, food could be obtained easily, and plenty of time would be left over for leisure tasks.