As of 1778, Thomas Kitchin described Chiapas as "the metropolis of the original Mexicans," with a population of approximately 20,000, and consisting mainly of indigenous peoples. The Spanish introduced new crops such as sugar cane, wheat, barley and indigo as main economic staples along native ones such as corn, cotton, cacao and beans. Livestock such as cattle, horses and sheep were introduced as well. Regions would specialize in certain crops and animals depending on local conditions and for many of these regions, communication and travel were difficult. Most Europeans and their descendants tended to concentrate in cities such as Ciudad Real, Comitán, Chiapa and Tuxtla. Intermixing of the races was prohibited by colonial law but by the end of the 17th century there was a significant mestizo population. Added to this was a population of African slaves brought in by the Spanish in the middle of the 16th century due to the loss of native workforce.