Pretty few Mayan and Aztec books survive to the present day, but they testify to(1) high cultural significance for avocados. The fourteenth month of the Mayan calendar [yes, it was quite different than ours!] was represented by the glyph [writing symbol] for... avocado! The Aztecs believed they gave strength to those who ate them(1,2) and was a plain source of nourishment in ancient Central America(2). They indeed include various nutrients as B vitamins plus some other vitamins and minerals(1). [Now, of course, avocado oil is coming into vogue as a healthy alternative oil.] "Avocados are part of the name glyph of the classic Maya city of Pusilhá in Belize, known as the 'Kingdom of the Avocado'."(1) "By 1521, the fruit had spread through Central America and into parts of South America before being exported back to Europe by the Spanish and sold to other countries."(2)
Three different main varieties of avocado came into separate existence in different parts of Central America sometime by the 1500s - Native Central American writings definitely describe all three. Mexican avocados are a smaller, purple-black, thin-skinned, relatively cold-tolerant highland type from Central Mexico. Guatemalan avocados from the south of Mexico into Guatemala are more suited for medium tropical elevations, have thicker skin, and have different seed shape but otherwise share Mexican avocados' size, shape, and some relative cold tolerance. "West Indian" avocados (really from lowland Central America) are the biggest, have an easy-to-peel green skin, and are a little sweeter-tasting. There are now 30 main cultivars [note: different term than a variety] in modern distribution. Hass avocados, a Mexican-Guatemalan variety hybrid, are the most-produced, accounting for about a third of the global market, Mexico being the biggest exporter, and the US being the biggest importer(1).
References:
1. Maestri, Nicoletta. "Avocado History - Domestication and Spread of Avocado Fruit:
What Scientists Have Learned about the History of the Avocado." ThoughtCo. Dotdash. 3 Jul. 2019. Web. 7 Apr. 2021. https://www.thoughtco.com/domestication-and-spread-of-avocado-fruit-169911.
2. "A History of Avocados." Avocados from Mexico. avocadosfrommexico.com. Web. 7 Apr. 2021. https://avocadosfrommexico.com/avocados/history/.