About 5,000 years ago, avocados went on an excellent adventure. Humans who migrated north toward Nicaragua from parts of South America brought avocado seeds and then planted the fruit in the humid lowlands of Central America. The avocados were then hybridized with native varieties, producing a wide range of large avocados with smooth skin and still enjoyed in the region today.

While they may look like the avocados we love in our guacamole, they are genetically distinct from the commercially grown fruits found at your local supermarket. This genetic difference and migration is detailed in a study published today in the journal Plants, People, Planetand shows the great diversity of these delicious green fruits.

“What’s quite fascinating about Nicaraguan avocados is that they look quite similar to those you can find in supermarkets in humid areas around the world, such as in Florida or the Caribbean,” says Kevin Wann, co-author of the study and an archaeologist at the Smithsonian’s National Museum of Natural History. popular science. “Despite their apparent similarity to other tropical avocados, the ones I collected comprise a completely different genetic lineage.”

That guacamole is made from clones.

avocado trees (American Persea) extend naturally from southern Mexico to Peru. For more than 10,000 years, humans have eaten the plant’s fruit, which is loaded with vital fats and nutrients. Considered a “superfood,” avocados are now grown all over the world. Growers produced more than 11 million metric tons of avocados in 2024 alone.

More than 80 percent of these avocados were of a single variety known as the Hass avocado (American Persea ‘Hass’). Large, long-lasting avocados are produced through a process called clonal grafting. A branch is removed from a 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 a change in temperature or rainfall patterns can wipe out an entire population of Hass avocados.

Increasing this genetic diversity of avocados is crucial to protecting this multi-billion dollar industry. To find genetically different varieties, Wann points to the muggy lowlands of Nicaragua and Honduras. For thousands of years, traditional agricultural practices have perfected the region’s native avocado varieties, also known as landraces.

“As I began to learn more about the interaction between culture and genetics as it relates to domestication, it became increasingly obvious that our understanding was biased by looking only at commercial cultivars and ignoring the importance of local varieties,” explains Wann.

Food poisoning, wasp sting and an exciting novelty

Wann and his team collected leaf samples from several varieties in southern Mexico, Nicaragua and coastal Honduras. And his work required dedication. Wann suffered attacks of food poisoning and was even stung on the face by a wasp during field work in southern Mexico.

However, he also ate an avocado for the first time. A farmer who took the team to tour a grove in Nicaragua offered them a piece of fruit.

“I wanted to see how far I could get in my thesis studying avocados without even eating them,” he said. “I did it for four years, but when one of the native farmers offered me one, I couldn’t turn it down.”

The team also interviewed local gardeners and rural farmers in Nicaragua and Honduras to learn more about the native avocado varieties they grow. This agricultural perspective was crucial, according to study co-author Logan Kistler.

“You can’t think about biodiversity without considering agriculture, because it is 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.”

Local farmers confirmed that these local lowland avocado varieties had not experienced root rot, which is the most common disease affecting commercial avocados. Some Nicaraguan farmers also graft commercial avocado branches onto native avocado trees, as native trees are better adapted to the local environment.

Genes point to major migration

Back in the lab (and away from the wasps), the team extracted and analyzed DNA from harvested leaf samples. They collected DNA from 47 native avocado varieties (32 of which came from Nicaragua) and compared the DNA of the different varieties with genetic data available from more than 200 other avocado lineages.

The team found that avocado samples collected in southern Mexico were closely related to ancestral highland avocado populations found in other parts of Mexico and in commercial varieties. By comparison, local varieties found in the lowlands of Nicaragua were genetically linked to avocados found further south, including along the coast of Colombia.

This genetic data revealed that local varieties in this part of Central America are planted from fruits originally grown in South America. The team believes that human populations brought their local varieties of avocado with them as they migrated through the Americas. The relocation of the avocado probably occurred around 4,000 to 5,000 years ago, which is when other South American crops, such as chocolate and some varieties of corn, appear in the archaeological record of Central America.

“Interactions between cultures in Central and South America skyrocketed [at this time]mainly thanks to the increase in corn cultivation,” says Wann. “This triggers a massive exchange of plant resources throughout Latin America, and this is an ongoing process, not just a one-time movement. Unfortunately, Central America is an underexplored area archaeologically, mainly thanks to a tropical environment where artifact preservation is poor and a scholarly preference for Mexico and South America.”

Protecting a popular fruit

This ancient avocado diversity preserved in the Central American lowlands could help protect current crops. Other clonal crops (those grown asexually from cuttings or grafts rather than seeds) have been devastated by pathogenic fungi. For example, bananas could become extinct due to a fungal disease called Fusarium banana wilt (FWB), which blocks the flow of nutrients and causes them to wilt. The pathogen even caused Gros Michel bananas to become functionally extinct in the 1950s.

The region’s local varieties are also adapted to warmer, wetter climates, which are increasing due to climate change.

“A plant like the avocado, so important to our global diet, is always subject to climate change, especially for a fruit whose main exports come from a single clone,” says Wann. “History has shown us that a single new disease is enough to devastate an entire plant market when overly dependent on such small genetic diversity. Conservation of genetic resources is the best way to counter unknown climate threats, and understanding them is always a great first step.”

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