Dear Kristen,

This answer is fueled by coffee with a splash of milk from a dairy cow.

I asked my friend Kimberly Davenport why my morning milk doesn’t come from a beef cow. She’s an expert in cow genetics at Washington State University.

She told me that all cows are the same species: Bos taurus. But different kinds of cows have different traits—like making lots of milk or growing big muscles.

“Over time, we’ve selected these cows to either make more milk or more meat,” Davenport said.

Selecting means noticing the traits you like and keeping animals with those traits. When those animals reproduce, … » More …