- Observations such as these were the foundations for the theory of evolution, which suggests that species were not fixed for ever but changed with time and thereby contribute to the immense diversity of life 0.5 Mb. 10
Ancient people of the southwest Audio: The Ancient Aztecs who traveled north to trade refer to it as Aztlan. Early Spanish explorers call it Pimeria Alta. Mexicans in the early nineteenth century named it El Norte and it was only after the Mexican-American War of 1848 that this region became known 139.02 Kb. 1