Meet the Researcher Studying How Ancient Human Migrations Shaped a Hotbed of Avocado Diversity in Central America

While collecting avocado leaf samples in Nicaragua, archaeobotanist Kevin Wann finally tasted the fruit he has spent years studying

Around 5,000 years ago, people migrating north from South America carried the oversized seeds of one of their favorite fruits—avocados. As these seeds were dispersed throughout the humid lowlands of Central America, they hybridized with native varieties, producing an array of avocados that produce the large, smooth-skinned berries that are now enjoyed around Central America.

A team of researchers recently found evidence of this ancient migration in the genetics of avocado plants in Nicaragua. Their findings, published this week in the journal Plants, People, Planet reveal that while the local varieties resemble the avocados found in humid regions like Florida and the Caribbean, they are more closely related to avocados growing in South America. They are also genetically distinct from the commercially grown fruits found in most guacamole.

The work was led by archaeobotanist Kevin Wann, who conducted the research during a research fellowship at the National Museum of Natural History with Logan Kistler, the museum’s curator of archaeobotany and archaeogenomics and a senior author on the new paper. Wann, who is currently getting his doctorate at Texas A&M University, analyzed DNA in avocado leaf samples from Nicaragua, Honduras and southern Mexico and spoke to local farmers and gardeners to learn about the varieties they grow. During one of these interactions, Wann tasted an avocado for the first time.

Wann recently spoke to Smithsonian Voices about his research, the implications of the new finding and his first avocado taste test. The interview has been edited for clarity and length.

How did you become interested in researching avocados?

I went into graduate school knowing that I wanted to study plant domestication through the DNA of traditional cultivars and archaeological genomes, but my sights weren't really set on any one specific plant at first. Most of my background before then was in Mexico and Central America, so that was the region that I was most interested in.

My advisor at Texas A&M University, Heather Thakar, is investigating plants across Central America and one of the species she was really interested in were avocado trees. That sounded awesome to me and I jumped at the opportunity to study avocados.

I was surprised to learn that you had never tried an avocado before this project. What took you so long?

When I began working on the project, I realized I had never really had an interest in trying an avocado or guacamole. I remember thinking, ‘Wait a minute, have I never even eaten an avocado before?’ From then on, I wanted to see if I could go through my entire dissertation studying avocados without ever having eaten one.

I went four years without having eaten an avocado, and then I did this project where I was interviewing local farmers and collecting roadside avocado leaf samples to do genetic analyzes on them. And one of the farmers that I interviewed said, ‘Here's a native avocado fruit, you should try it,’ and I couldn't say no.

What did you think of the taste of your first avocado?

I was not expecting the flavor when I first had it and was initially pretty surprised. But I like the taste now and think they’re delicious. I now eat guacamole all the time.

What sparked your interest in investigating avocados in this part of Central America?

In the summer of 2022, I participated in a field archaeology project in northwest Nicaragua. As we were doing the excavations, I noticed the sheer variety of different kinds of avocado trees growing there, and I thought it'd be really cool to learn more about them. I wanted to do a broad sampling of their local avocado varieties to learn more about where Nicaraguan avocados came from and what they can tell us about local biodiversity.

"You have to actually go there and learn from the people who are most familiar with these plants to get a broad understanding."
— Kevin Wann, Archaeobotanist

In 2024, I participated in another archaeology expedition here and was able to take day trips to collect samples of different avocado trees and interview local farmers. And I was able to compare them to samples collected in Honduras by one of my collaborators and some samples I collected in southern Mexico.

Were you surprised that some of these local avocados were so different from commercial varieties?

It definitely was a surprise because of how similar they look to ones that we find at grocery stores. There are a few main varieties of avocados. There are the kinds that are grown in cooler, higher environments. Those are the ones that I was able to find growing in southern Mexico. And there are ones that are more adapted to the lowland, tropical, super humid, super rainy regions like tropical Nicaragua.

These avocados from the lowlands resemble commercial varieties grown in other tropical places like Florida or the Caribbean and produce really big fruit. However the Nicaraguan avocados are substantially different from those found in Florida from a genetic perspective. The similarities in fruit size and appearance are just from growing in similar environments.

Why were interviews with local farmers and gardeners so important for the project?

To understand the history and biodiversity of a crop species, you really need to explore the combination of genetics, ethnography and anthropology. This work is multidisciplinary. You have to actually go there and learn from the people who are most familiar with these plants to get a broad understanding.

How did the movements of ancient people throughout the Americas help create the avocado diversity seen in Central America today?

There are some Nicaraguan avocados that share a common ancestor with South American avocados instead of other Nicaraguan ones. And one very strong explanation for this idea is that people brought avocados with them during ancient migrations from South America to Central America.

A northern migration from South America is very well documented in a lot of other plant species. For example, we have good evidence for the northern migration of South American varieties of corn and other plants like cassava.

People were probably going back and forth along trade routes throughout the past several thousand years. Cultures were becoming more interconnected, especially through the development of farming and the expansion of larger communities. That's always going to include the exchange of more foreign varieties of plants and crops, and avocados is just one of many.

Why is better understanding the history and diversity of avocados so important?

The vast majority of commercial avocados are clones of one variety known as the Hass avocado. It's grown and exported everywhere. Hass avocados account for around 80 to 90 percent of avocados worldwide.

Because they are genetic clones, they are susceptible to the same things. Let's say there happens to be a disease that arises that is really effective at killing the Haas avocado. That would decimate global avocado production. That exact thing happened with bananas. There was a huge blight that targeted the Cavendish banana variety and it devastated banana production worldwide.

So it's important to have a good idea of the total diversity of avocados that exist anywhere, especially in the native region, where diversity is going to be the highest. If the worst were to arise, we need to know what other avocado lineages are out there.

Thankfully, this research shows that there is a much wider breadth of avocado diversity that we had not yet documented. This diversity of avocados could be implemented for conservation efforts if the need ever arises.

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Jack Tamisiea | | Read More

Jack Tamisiea is a Science Communications Specialist at the Smithsonian's National Museum of Natural History. In addition to covering all things natural history for the museum's blog, Smithsonian Voices, he tracks media coverage and coordinates filming activities for the museum's Office of Communications and Public Affairs. Jack recently completed his masters in science writing at Johns Hopkins University and his writing has appeared in the New York Times, Scientific American, National Geographic and other science-focused publications. In his free time, he loves exploring the outdoors with a sketchbook and camera. You can read more of Jack's work at https://jacktamisiea.com.