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About 5,000 years ago, avocados went on an excellent adventure. Humans migrating north towards Nicaragua from parts of South America brought avocado seeds and then planted the fruit in Central America’s humid lowlands. The avocados then hybridized with the native varieties, producing a wide range of avocados that are large with smooth skin, and still enjoyed in the region today.
While they may look like the avocados we love in our guacamole, these are genetically distinct from the commercially grown fruits found at your local grocery store. This genetic difference and migration is detailed in a study published today in the journal Plants, People, Planet, and shows the vast diversity of these delicious green fruits.
“What’s pretty fascinating about Nicaraguan avocados is that they look pretty darn similar to ones you might find in supermarkets in humid areas across the globe, like in Florida or the Caribbean,” Kevin Wann, a study co-author and archaeologist with the Smithsonian’s National Museum of Natural History, tells Popular Science. “Despite their apparent similarity to other tropical avocados, the ones that I collected comprise a completely different genetic lineage.”
That guac is made of clones
Avocado trees (Persea americana) naturally extend from Mexico south to Peru. For over 10,000 years, humans have eaten the plant’s fruit that is loaded with vital nutrients and fats. Considered a “superfood,” avocados are now cultivated around the world. Growers produced more than 11 million metric tons of avocados in 2024 alone.
Over 80 percent of these avocados were a single variety known as the Hass avocado (Persea americana ‘Hass’). The large and long-lasting avocados are produced through a process called clonal grafting. A branch is removed from one Hass avocado tree and then attached to another tree to bear the same fruit. As a result of this cloning process, most avocados you see in a grocery store or restaurant are genetically indistinguishable. This lack of genetic diversity makes Hass avocados vulnerable to the same threats. One disease or change in temperature or rain patterns can wipe out an entire population of Hass avocados.
Increasing this genetic diversity of avocados is crucial to protect this multi-billion-dollar industry. To find genetically different varieties, Wann points to the muggy lowlands of Nicaragua and Honduras. Over thousands of years, traditional agricultural practices have fine tuned the region’s native avocado varieties, also known as landraces.
“As I began learning more about the interplay between culture and genetics as it pertains to domestication, it became increasingly obvious that our understanding was biased by only looking at commercial cultivars and ignoring the significance of landraces,” Wann explains.
Food poisoning, a wasp sting, and an exciting first
Wann and a team collected leaf samples from several varieties in southern Mexico, Nicaragua, and coastal Honduras. And his work took dedication. Wann had bouts of food poisoning and was even stung in the face by a wasp during field work in southern Mexico.
However, he also ate an avocado for the first time. A farmer giving the team a tour of a grove in Nicaragua offered him a piece of the fruit.
“I wanted to see how far I could go into my dissertation studying avocados without ever eating one,” he said. “I made it four years, but when one of the native farmers offered me one, I couldn’t turn him down.”
The team also interviewed local gardeners and rural farmers in Nicaragua and Honduras to learn more about the native avocado varieties they cultivate. This agricultural perspective was crucial, according to study co-author Logan Kistler.
“You can’t think about biodiversity without considering agriculture, because it’s one of the most impactful ecological activities we do,” Kistler, the museum’s curator of archaeobotany and archaeogenomics, said in a statement. “Traditional agricultural practices have shaped these plants for thousands of years.”
The local farmers confirmed that these lowland avocado landraces had not experienced root rot, which is the most common disease affecting commercial avocados. Some Nicaraguan farmers will also graft commercial avocado branches onto native avocado trees, since the native trees are better adapted to the local environment.
Genes point to a major migration
Back in the lab (and away from wasps), the team extracted and analyzed DNA from their harvested leaf samples. They collected DNA from 47 native avocado landraces (32 of which came from Nicaragua) and compared the DNA from the various landraces with available genetic data from more than 200 other avocado lineages.
The team found that the avocado samples collected in southern Mexico were closely related to the ancestral highland avocado populations found in other parts of Mexico and in commercial varieties. By comparison, the landraces found in Nicaragua’s lowlands were genetically tied to avocados that are found further south, including along the coast of Colombia.
This genetic data revealed that the local landraces in this part of Central America are planted from fruits originally grown in South America. The team believes that human populations brought their local avocado varieties with them as they migrated throughout the Americas. The avocado relocation likely occurred around 4,000 to 5,000 years ago, which is about when other South American crops, like chocolate and some maize varieties, appear in the Central American archaeological record.
“Interactions between cultures across Central and South America skyrocketed [at this time], mostly thanks to increased corn farming,” says Wann. “This sparks a mass exchange of plant resources throughout Latin America, and this is an ongoing process, not just a single movement. Unfortunately, Central America is an under-explored area archaeologically, mostly thanks to a tropical setting for poor artifact preservation and a scholarly preference for Mexico and South America.”
Protecting a popular fruit
This ancient avocado diversity preserved in Central America’s lowlands could help protect today’s crops. Other clonal crops—those cultivated asexually from cuttings or grafting rather than from seeds—have been devastated by fungal pathogens. For example, bananas could go extinct from a fungal disease called Fusarium wilt of banana (FWB), which blocks the flow of nutrients and makes them wilt. The pathogen even made Gros Michel bananas functionally extinct in the 1950s.
The region’s local landraces are also adapted to warmer and wetter climates, which are both increasing due to climate change.
“A plant like the avocado, which is so important to our global diets, is always subject to climate change, particularly with a fruit whose main exports come from a single clone,” says Wann. “History has shown us that just one new disease is enough to devastate a plant’s entire market when there’s an over-reliance on such a small genetic diversity. Conservation of genetic resources is the best counter to unknown climatic threats, and its awareness is always a great first step.”
