<P> Accounts written by the Spanish at the time of their conquest (the conquistadores) and by indigenous chroniclers of the post-conquest period constitute the principal source of information regarding Mexico at the time of the Spanish Conquest . </P> <P> While relatively few pictorial manuscripts (or codices) of the Mixtec and Aztec cultures of the Post-Classic period survive, progress has been made in the area of Maya archaeology and epigraphy . </P> <P> The presence of people in Mesoamerica was once thought to date back 40,000 years, an estimate based on what were believed to be ancient footprints discovered in the Valley of Mexico; but after further investigation using radiocarbon dating, it appears this date may not be accurate . It is currently unclear whether 23,000 - year - old campfire remains found in the Valley of Mexico are the earliest human remains uncovered so far in Mexico . </P> <P> The first people to settle in Mexico encountered a climate far milder than the current one . In particular, the Valley of Mexico contained several large paleo - lakes (known collectively as Lake Texcoco) surrounded by dense forest . Deer were found in this central area, but most fauna were small land animals and fish and other lacustrine animals were found in the lake region . Such conditions encouraged the initial pursuit of a hunter - gatherer existence . </P>

Mexico was a colony of what country for three hundred years