Animals.

As a concept, they become less prominent in your mind as you age (exception being pets).

A 12 year old is clearly much more likely to be thinking about e.g. zebras, orca whales, tigers, etc. than a 30 year old.

Lesson in there.

I think this an innate and universal part of being human, for most of human history learning about animals and your immediate natural environment was essentially to your survival, so childhood curiosity about nature is programmed in.

Scary and sad to think about a future of biodiversity loss and children learning about rhinos or koalas in the same way we learnt about dodos or woolly mammoths.