Recorded actions come first; the conclusions below are interpretations, not claims about private intention.

Ant-dipping stick

Recorded

Soukki inserts stick›Brings Saïsaï to it›Infant extracts and eats ants

Behavior changed?: Yes: the prepared tool was made available to the infant.
Cost or lost advantage?: Time and immediate access were given up; no clear immediate gain was reported.
Learner opportunity?: Immediate access to a difficult technique and food.

Strong functional fitThe actions rearranged the task so the infant could succeed.

Baobab at the anvil

Recorded

Juvenile pounds fruit›Guides Fotti’s hand›Infant tries and succeeds

Behavior changed?: Yes: the juvenile physically directed the infant toward the fruit.
Cost or lost advantage?: Unclear: the juvenile later obtained food, so interests may have overlapped.
Learner opportunity?: Demonstration, guided contact, practice and successful imitation.

Suggestive, but ambiguousTeaching, play and self-interested fruit handling remain plausible.

The boundary: Evidence that help improved learning can satisfy a functional definition of teaching. It cannot, by itself, establish what the helper meant or understood.