Puzzlement

He frowned in puzzlement.

His face betrayed his sheer puzzlement.

Ziri scratched his head in puzzlement.

The puzzlement caused by the complex system led to great anger.

Or, larger mothers might have not necessarily more progeny but more fit ones, while smaller size might be an advantage to the males, allowing them to get around faster. Finally, for creatures that continue to grow, perhaps more of the females simply live longer, gaining in stature all the time. “'Tis a puzzlement.”

The diary contains plenty of small puzzlements.