Now, a few tens of thousands of years ago, wolves and people started becoming friendly species.

You can imagine a person tossing a bone to a friendly wolf from time to time.

But “friendly” is the key.

Nobody ever gets close to a hostile wolf.

So over many thousands of years we would have been gradually selecting for certain behavioral traits-playfulness, low hostility, the ability to bond.

Very puppy-like behaviors! See what's happening?

A species that resembles a wolf puppy that never grows up may have slowly evolved in this way.

That species would retain its puppy-like behaviors, such as barking, but never grow into growling, howling adult wolves.

That species We would now call that species “dogs.”