2 plants randomly mated up to 1 million years ago to give rise to one of the world's most popular drinks

The plants that provide most of the world's coffee supply emerged around 600,000 to 1 million years ago when two other species of coffee cross-pollinated in the forests of Ethiopia, scientists have discovered. 

About 60% of the world's coffee supply is sourced from Coffea arabica plants, which now grow in tropical regions across the world New research, published April 15 in the journal Nature Genetics, has revealed when and where the original C. arabica plants likely developed. 

Using population genomic modeling methods, the researchers determined that C. arabica evolved as a result of natural hybridization between two other species of coffee: C. eugenioides and C. canephora. The hybridization resulted in a polyploid genome, meaning each offspring contains two sets of chromosomes from each parent. This may have given C. arabica a survival advantage that enabled it to thrive and adapt.

"It's often argued that a hybrid polyploidy event can give an immediate evolutionary advantage given that two sets of chromosomes — and therefore two complete sets of genes — are inherited immediately after," study co-author Victor Albert, a biologist at the State University of New York at Buffalo, told Live Science. "Of course, it's always the case that duplicate genes are lost on the two genome halves of the polyploid, but there is always a net gain in gene numbers and therefore, possibly, a greater capacity to adapt to new environments."

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The researchers acknowledge that there is a margin of error. Earlier estimates of the time of hybridization date it as recently as 10,000 years ago. 

"We had to input an estimated mutation rate, and a generation time (seed to seed time). Together, these assumptions allow us to convert to calendar years. But these estimates are of course fraught with error ranges given the usual uncertainty on mutation rates and generation times," Albert said. Still, he thinks their estimate is reasonably accurate. The researchers used genetic information from 41 samples of C. arabica from various locations, including an 18th-century specimen.