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Fossil evidence found of humans domesticating avocados 7,500 years ago

A team of anthropologists and evolutionary biologists affiliated with several academic institutions in the U.S., working with a colleague from the Smithsonian Institution, has found evidence of humans domesticating avocados as far back as 7,500 years ago in what is now Honduras.

In their paper in the Proceedings of the National Academy of Sciences, the group describes their analysis of more than 1,700 fossilized avocados retrieved from a dig site in Honduras and what they learned during their efforts.

Avocados grow naturally on tropical evergreen trees in parts of South and Central America and Mexico—they have also been migrated to farms in many other parts of the world. Prior research has shown that their earliest appearance was approximately 400,000 years ago in Mexico, and over the next several thousand years, they split into three species.

For most of their history, their seeds were dispersed by megafauna. Their numbers fell dramatically during a megafauna extinction at the end of the Pleistocene, but picked up again with the appearance of humans, who likely saved them from extinction. In this new effort, the researchers sought to learn more about their history after humans began using them as a food source.

The work by the team involved analyzing 1,725 fossilized avocado samples that had been pulled over many years from a dig site at El Gigante rockshelter in what is now Honduras. They found they were able to date 56 of them to certain points in time, going back approximately 11,000 years.

The researchers could see that the rinds of the fruit grew thicker over time. They also found that seed size grew over the same period. They suggest such changes are indicative of domestication by humans, who preferred larger fruit. They also found evidence suggesting that domestication began through managing wild trees and then eventually through planting seeds from fruit with the most desirable traits.

The evidence showed domestication starting as early as 7,565 to 7,265 years ago. The researchers also note that their findings show avocados were being domesticated thousands of years before other crops, such as maize.