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article imageChocolate's sweet beginnings are older than first thought

By Karen Graham     Nov 11, 2015 in Science
New research suggests it took geological events and a genetic tweak over 10 million years ago to give us the velvety chocolate treats the world enjoys today.
The new study shows us the source of chocolate, the cacao tree, Theobroma cacao, has a far greater genetic diversity in the wild than previously thought.
"We show for the first time that the source of chocolate, Theobroma cacao, is remarkably old for an Amazonian plant species," the study's lead author, James Richardson, a tropical botanist at the Royal Botanic Garden Edinburgh, Scotland, said in a statement, reported by Live Science.
From cacao pods to chocolate bars
The chocolate we know and love goes through an arduous process before it becomes a piece of candy or the hot concoction we drink with little marshmallows floating on top. From the cacao pod, processing includes fermenting, drying and roasting the pulp, grinding cocoa nibs, extracting and reintroducing cocoa butter and mixing in sugar and milk.
Rather than relying on wild cacao trees, the majority of cacao trees are grown as crops to satisfy the world's $100 billion sweet tooth, say researchers, and the cacao trees are genetically very similar. As we have seen, genetically homogeneous crops are susceptible to disease, and population collapse. This very thing happened with bananas.
In the 1950s, according to a report in Digital Journal in June, the world's top-selling banana, the Gros Michel banana met its demise due to a fungal disease. The industry had to switch to the Cavendish variety.
But banana plants are clones, all derived primarily from a single plant in Southeast Asia. Cacao trees are different in that respect. The researchers found that cacao trees had a little help from geography. They found that the Theobroma genus diverged from its closest cousin, Herrania, about 12.5 million years ago, right about the time the Andes mountains began to rise.
The trees were able to grow on both sides of the mountain range because they were not yet tall enough to prevent the trees' spread. Herrania is a genus of flowering plants and is closely related to the genus Theobroma, a member of the Malvaceae family, which includes okra, cotton and cacao.
It wasn't until a few million years later that scientists believe the two parted ways, based on ongoing geologic events that affected species diversification, according to the study.
Cacao trees originated in South America
The research team expressed surprise at discovering the cacao tree did originate in South America. "After 10 million years of evolution, we should not be surprised to see a large amount of variation within the species, some of which might exhibit novel flavors or forms that are resistant to diseases. These varieties may contribute towards improving a developing chocolate industry," Richardson said.
The research suggests there are still cacao trees lurking in the Amazon forests that could provide enough genetic variance to help fight off disease in the future. The study also suggests at least one temperate lineage within the family diverged from tropical ancestors then diversified at a rate comparable with many tropical lineages in the family.
This study, "The age of chocolate: a diversification history of Theobroma and Malvaceae," was published in the online journal Frontiers in Ecology and Evolution on November 10, 2015.
More about chocolate's origins, amazonian plant species, cacao pods, cavendish banana, 10 million years
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