On the forty first day of the flood, when it ended, the animals began to disembark in the same pairs by which they had first set off. But the Cat and the Dog did not wish to leave Noah, which is why they are our pets. And the Canadian Mallard had married the Beaver, which is why we have the platypus. And all were afraid of being caught surprised by another great rain, which is why Noah invented the weatherman. And the animals did not know where the one began and the other ended, which is why we are separated from each other. And many of the animals wished to return to another and escape their loneliness, which is why we enter each other in passion and hug each other so tightly. And many did not know when to sleep, which is why the sun sets. And many animals did not like their jobs, which is why we can quit. And many of the animals did not wish to stay together, which is why there is a zoo in Central Park.
From this, and many more things, is where it all comes from.