We used to think that humans were the only animals to use tools, but this was disproven long ago: otters use rocks to break open shellfish, birds use tools to create their nests, etc.

Then, we thought that humans were the only animals to fashion tools, not merely pick up objects from their environment. This was also disproven. Primates sharpen sticks to hunt, bend twigs to get ants out of trees, etc.

Today, we believe humans' unique relationship to tools is recursive: we're the only animal ever observed to use a tool to make a tool.

It's this capacity for self-referential thought that sets us apart from the rest of the creatures on earth.

There's tremendous intelligence in the animal kingdom: Octopuses and crows can solve complex problems, dogs can manipulate humans, dolphins can transmit visual imagines to one another through sound.

But self-referential thought is why a human built this website and other animals could not.