It is easy to see basic evolution at work. Farmers use selective breeding to change the look and body of animals every day.
http://www.crazyforcows.com/fow/fow28.shtml
http://www.tsha.utexas.edu/handbook/online/articles/view/LL/atl2.html
Fencing made possible controlled breeding, and with the end of free grass it was economically advisable to raise cattle that developed faster than longhorns. By this time ranchers had begun crossing longhorns with shorthorn Durhams and later with Herefords,[size=-1]qv[/size] thus producing excellent beef animals. Longhorns were bred almost out of existence; by the 1920s only a few small herds remained.
http://www.crazyforcows.com/fow/fow28.shtml
http://www.tsha.utexas.edu/handbook/online/articles/view/LL/atl2.html
Fencing made possible controlled breeding, and with the end of free grass it was economically advisable to raise cattle that developed faster than longhorns. By this time ranchers had begun crossing longhorns with shorthorn Durhams and later with Herefords,[size=-1]qv[/size] thus producing excellent beef animals. Longhorns were bred almost out of existence; by the 1920s only a few small herds remained.