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Avocados Were Domesticated 7,500 Years Ago According To Fossil Evidence

The ancient peoples of Latin America did us all a tremendous favor by saving avocados from extinction and gradually making them tastier over thousands of years of domestication.

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(Credit: Markus via Pexels / CC0, Public domain)Markus via a Creative commons license

Avocados, Persea americana, have been an important part of peoples’ diets throughout the Americans for thousands of years. A treasure trove of fossils unearthed from an ancient rock shelter in Honduras finds humans were eating avocados as long as 11,000 years ago, and they were actively farming avocado trees as early as 7,500 years ago. This discovery suggests that farming avocado trees prepared the Indigenous peoples of Central and South America to later grow domesticated field crops like corn.

“These people literally domesticated their forests,” said the study’s lead author, anthropologist Amber VanDerwarker, a professor in the Department of Anthropology at the University of California, Santa Barbara. Professor VanDerwarker is an expert in ancient plants and agriculture.

This discovery rewrites our understanding about the beginnings of farming. Originally, most experts thought ancient Indigenous Americans were hunter-gatherers until they discovered corn, and then they became farmers. But avocado farming apparently predated corn farming. For example, when corn first arrived “they already understood the whole notion of planting seeds and managing growth,” Professor VanDerwarker noted.

Professor VanDerwarker and collaborators made this discovery in an archeological deposit within the enormous El Gigante rock shelter found in southwestern Honduras. A rock shelter (also known as a rockhouse, or abri) is a shallow cave-like opening at the base of a bluff or cliff. Unlike caves, which can stretch for miles underground, rock shelters are almost always modest in size and extent by comparison.

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The El Gigante Rock Shelter is located on a volcanic plateau along the Estanzuela River at an elevation of 1,300 meters (Figure 1A). The site was first excavated beginning in 1995, and in 2018, scientists began collecting, analyzing and radiocarbon dating fossils unearthed from El Gigante rubbish piles.

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Figure 1 doi:10.1073/pnas.2417072122

Fig. 1. (A)–Map of Central and northern South America, showing the presumed native ranges of major

This archaeological site is exceptional because of how long people continuously lived there and due to its wealth of ancient kitchen scraps.

The El Gigante rock shelter itself is more than 120 feet wide and 55 feet deep, and contains trash piles left by its former residents that span the last 11,000 years. These rubbish heaps are rich in paleobotanical fossils, including fragments of more than 20,000 plants such as avocados, bottle gourds, agave, beans and squashes. These garbage piles are providing scientists with a fascinating glimpse of the occupants’ changing resource utilization and economic patterns over the past 10,000 years. Further, they are providing an incredibly rare opportunity to examine the evolutionary history of plant domestication.

To better understand the process of avocado domestication, Professor VanDerwarker and collaborators assembled 1,725 avocado fossils, including rinds and pits, to study changes in the shape and size of the fruits over time. Of all the fossils that they radiocarbon dated, Professor VanDerwarker and collaborators were able to date 56 of them to specific points in time, over a time period reaching back approximately 11,000 years.

They found that, during the domestication process, avocado rinds became thicker, the pits larger, and the amount of the edible flesh increased. Professor VanDerwarker and collaborators argue that these changes indicate domestication by humans, who preferred larger fruit. They also found evidence suggesting that domestication began by managing the wild trees themselves, then eventually by planting seeds from fruit with the most desirable traits.

avocado-cut-diet-food-preview (via PikPik / CC0, public domain)

During domestication, avocado rinds became thicker, the pits larger, and the amount of the edible ... [+]via PikPik via a Creative Commons license

Avocados have an interesting evolutionary history since they first arose in central Mexico about 400,000 years ago. Pleistocene mammalian megafauna, such as giant ground sloths, gompotheres and toxodons, swallowed the fruits whole, and acted like a taxi service for relocating avocado seeds across the countryside. Avocados’ dependence upon megafaunal dispersion almost led to their undoing when all of these large mammals suddenly went extinct around 12,500 years ago due to human hunting, possibly also combined with environmental or climactic effects. However, by this time, humans had discovered the joys of eating avocados and in doing so, likely saved them from extinction by cultivating and domesticating them as a food source.

How does the process of domestication differ between animals and plants?

“The process of domestication for plants and animals is similar in that people have to control space, breeding, and feeding,” Professor VanDerwarker told me in email.

Not all plants and animals are domesticated (zebras versus horses are famous examples), so what traits are possessed by a good candidate for domestication?

“Good candidates are genetically malleable to human manipulation and adaptable to human-disturbed environments,” Professor VanDerwarker explained in email. “For me, the difference that is notable in this particular case is not between plants and animals, but between annual plants and perennial plants. Annual plants like maize have to be planted every year, so seed selection happens every year, which means domestication can potentially happen rapidly. Trees, like avocados, however, have a much longer reproductive span from planting to producing fruits.”

Female_resplendent_quetzal_eating_a_wild_avocado

A female resplendent quetzal (Pharomachrus mocinno) dines on a wild avocado (Persea americana) in

“Thus, the ways in which humans developed field versus forest agriculture must have been very different,” Professor VanDerwarker explained in email. “Indeed, our data show that people were eating avocados for at least 5500 years before evidence of domestication; our data show that people were managing trees for fruit size (likely through thinning and pruning) 3000 years before evidence of domestication; and our data show that people had domesticated avocados in Honduras BEFORE maize arrived (fully domesticated) at the site.”

What surprised you most about this study’s findings?

“The fact that avocados were fully domesticated before domesticated maize reached the site,” Professor VanDerwarker replied in email.

“Maize was domesticated in somewhat arid western Mexico (Guerrero). Avocados (and other tree fruits) were domesticated in the Central American Neotropics.”

Consequently, understanding the intricacies of Mesoamerican agriculture is much more complicated than scientists originally thought.

“Two very different environments. Parallel developments of indigenous groups slowly gaining expert familiarity with local plants, managing their growth, experimenting with two very different systems of cultivation,” Professor VanDerwarker replied in email.

“It’s clear that in Mesoamerica, avocados are as integral to understanding the development of agriculture as maize.”

Further, the Americas lacked domesticated food animals, so the indigenous peoples relied on insects, fishing, and hunting wild game to obtain protein & fat in their diets – “but wild animals are much leaner than domesticated animals,” Professor VanDerwarker pointed out.

“Avocados make up for this fat deficit as an amazing source of poly-unsaturated fats,” Professor VanDerwarker explained in email. “It’s a perfect food for foragers and subsistence farmers. It’s a perfect food for us!”

Source:

Amber M. VanDerwarker, Heather B. Thakar, Kenneth Hirth, Alejandra I. Domic, Thomas K. Harper, Richard J. George, Emily S. Johnson, Victoria Newhall, Timothy E. Scheffler, Weston C. McCool, Kevin Wann, Brandon S. Gaut, Logan Kistler, and Douglas J. Kennett (2025). Early evidence of avocado domestication from El Gigante Rockshelter, Honduras, Proceedings of the National Academy of Sciences of the United States of America 122(10):e2417072122 | doi:10.1073/pnas.2417072122