Cows evolved from a single ancestor called the aurochs. The aurochs survived until the early 17th century when it went extinct after being hunted. Cows have several defining features like weighing over 450 kg and having a four-compartment digestive system. They can have horns or not depending on their breeding. Cows travel in herds of 10 to hundreds of members with one bull per cows. They are generally active in the mornings and afternoons.