These animals help us provide for our families and others, they've helped us survive throughout rough times. We've found many different uses for cows, goats and sheep. For example, they all produce milk, that contains the calcium and other vitamins we need. Their meet is not only very delicious, and nutritional, it's also a great source of protein. When we eat the meat we feel full, more than what we would feel if we only eat wheat and fruit. The fat of the pig might not be very healthy, for it has plenty of fat, but it sure kept us full as well. These animals are very easy to take care of, we didn't have much trouble domesticating them. Also, since all they eat is herbs, their excrement is used as good soil fertilizer, which is only helpful for us.
The skin of the cows, sheep and goats where very valuable as well, we could use their skin as clothing and blankets. As, we keep finding new ways of using these animals that didn't have to be fed meat (other animals); the number of these animals kept increasing. As well as our increase in technology. The use of fire to heat up the meat and cook it, also finding new ways of using their milk. We now use cow and goat milk, and other dairy products that are very profitable.
The horses are exceptionally important in our animal evolution and our human evolution. These animals have helped us in battles in the early days. They were a sign of power in many places. For example when the Europeans went to places like Mexico and Perú, they were viewed very differently. The Aztecs where frighten of these "monsters". Nevertheless, they were useful to carry out messages to other places, since technology wasn't as advanced as it is now.
Nevertheless, if humans started spreading from Mesoamerica and little by little moved west to Eurasia and Africa, it probably had been quite difficult to domesticate the animals specified above. Growing crops would have been a very slow process if we were to do it manually without the help of these animals. And to not mention animal domestication would have become very difficult.