Jeremy’s latest newsletter saves me including an interesting paper on the domestication of avocado in a forthcoming Brainfood.
The often humid climate of the tropics means that ancient plant remains are few and far between, making it difficult to trace the long-term history of crops there. Thanks to a dry rock shelter in western Honduras, which preserved “an unparalleled sequence of radiocarbon-dated avocado remains,” researchers have now rewritten its ancient history. The paper is paywalled; I found out about it because one of the universities involved has just published a popular account, which in turn led me to an earlier popular report from another of the universities.
Two key milestones emerged. First, people were tending wild avocado trees as far back as 11,000 years ago. And by 7500 years ago, they had begun to select for larger fruits with tougher skins. Those ages reveal a bigger surprise; they predate the arrival of maize. The standard view is that as maize spread to new locations, it transformed foragers into farmers. The new results show that people were “fully engaged in tree cultivation upon maize’s arrival”.
The research also has a message for the modern avocado industry, 90% of whose fruits are of the single Hass variety. Because they are multiplied as clonal offsets, those trees are all genetically identical and thus all equally vulnerable to any pest, disease or climate change that affects them. The researchers point out that farmers grew avocados from seedlings for millennia, and that much of that genetic diversity lingers in remaining relict populations. As Amber VanDerwarker, lead researcher on the study, points out:
Developing new varieties through seed selection of modern domesticates and wild relict populations growing throughout Central America may provide more success in adapting trees to these changing landscapes than clonal propagation alone.