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Cacao Trees, Chocolate and Steam-flowers

Cacao fruits at a cacao tree in Kerala, India.
Wikimedia Commons
Cacao fruits at a cacao tree in Kerala, India.

No chocolate fan has to wonder why the scientific name of the cacao tree translates from the Greek to "the food of the gods."

The tree evolved in the South American Andes. Nearly 4,000 years ago, the earliest chocolatiers were the Olmecs in southern Mexico. Later, the Mayans and Aztecs consumed chocolate in ceremonies and celebrations, and used cacao beans as currency.

In the 1500s, chocolate mania spread throughout Europe, where people added cane sugar, cinnamon and other flavorings. Today, cacao plantations cover over 25 million acres all over the tropics.

The complex process of changing cacao beans to chocolate bars starts by harvesting the fruit. Each pod holds about 40 bean-shaped seeds, surrounded by a white pulp. The seeds are fermented, dried, roasted, cracked and shelled. The resulting nibs are ground into cocoa butter and cocoa powder, and are finally combined with sweeteners to create the chocolate we love.

But what most interests me about the cacao tree is its unusual reproductive biology. Given the great glory of chocolate, the cacao tree is surprisingly small, crookedy and kind of unassuming, never growing much taller than 20 feet high.

And, unlike 99% of the other trees in the world, which sprout flowers and fruits from new shoots, cacao pods grow directly from the trunks and main branches, a growth pattern called cauliflory, from the Latin "stem flower."

Figs, papayas, jackfruit and redbuds are also cauliflorous. Why do some trees do this? Botanists speculate that the pattern evolved because the animals that disperse the cacao tree’s seeds, like 30-pound howler monkeys, are too heavy to reach fruit at the end of the tree’s slender branches. Cauliflory gives them solid support as they can move seeds to safe sites.

Today, as I look out my window at our snowy Utah landscape, I’m glad for whatever evolutionary pathway created this curious growth form — and provided me with a tasty cup of hot chocolate, created by the cacao tree.

Dr. Nalini Nadkarni is an emeritus professor of both The Evergreen State College and the University of Utah, one of the world’s leading ecologists and a popular science communicator. Dr. Nadkarni’s research and public engagement work is supported by the National Geographic Society and the National Science Foundation. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation. @nalininadkarni
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