This is a passenger announcement. You can now book your train on Uber and get 10% back in credits to spend on Uber eats.

So you can order your own fries instead of eating everyone else's.

Trains, now on Uber. T's and C's Science. I'm Suzanne Bard.

All domestic dogs belong to a single species that descended from wolves, despite vast differences in size, appearance, behavior, and temperament among breeds.

While dogs first became domesticated tens of thousands of years ago,

the breeds we know today are largely the result of selection for certain traits

by humans over the past several hundred years.

We have an enormous amount of diversity within the same species

and we can rarely observe such diversity in nature.

So it's a wonderful system to understand how evolution works within a short period of time.

Evolutionary biologist Lasslo Garam-Segi of the Institute of Ecology in Hungary.

He says that our playing with dogs is a key component of the human canine bond, but breeds

vary in their degree of playfulness.

For example, a breed called the Vishla is very playful.

On the other end, the Chihuahua doesn't like to play at all.

Of course you can train a little bit but the average level of

playfulness will be always lower than in the Hungarian Vigula.

Garam Saki and his colleagues analyze the playfulness of more than 89,000 purebred dogs across 132 breeds from

Pomeranians to Great Danes. The dogs were all given a test measuring their

degree of enthusiasm for a game of tug of war with people.

We were interested in whether breeds could be distinguished by their average level of

playfulness and what are the evolutionary forces that makes different breeds behave differently.

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