The largest population of Central America, spanning from Mexico to Colombia and Venezuela, is of Mestizo descent – a mixture of Spanish, Native American, and African ancestry. Puerto Rico and the Dominican Republic, interestingly, have a greater Caucasian population, representing European migration. In contrast, indigenous Central Americans are Mayans, the descendants of the advanced Mayan civilization of pre-Colombian times. Ancient Central American civilizations produced many important innovations, including pyramid construction, complex mathematical and astronomical observations, early forms of medical surgery, accurate calendar systems, and complex agricultural methods. In contemporary society, many people with Central American ethnicity have settled among the nations in South America, reaching as far south as Uruguay and Argentina.