Somewhere in the world, 71 cups of coffee are consumed every second of every day for a total of 2.25 billion cups per year. Worldwide the consumption of coffee provides 26 million jobs and $15.4 billion in exports, much of which goes to very poor coffee producing countries. Those numbers do not even take into account the consumption of tea, chocolate and other caffeinated beverages.

No one is sure, however, exactly why plants such as coffee, tea and cocoa produce caffeine in the first place. New research published in the September 5 edition of the journal Science provides new information, but also produces more mysteries.

“Coffee is as important to everyday early risers as it is to the global economy. Accordingly, a genome sequence could be a significant step toward improving coffee. By looking at the coffee genome and genes specific to coffee, we were able to draw some conclusions about what makes coffee special,” said Philippe Lashermes, a researcher at the French Institute of Research for Development (IRD), in a statement.

The newly sequenced genome of the coffee plant sheds light on the evolution of caffeine. Interestingly, the plants which produce caffeine appear to have evolved separately to produce the same chemical. In other words, coffee, tea and cocoa do not appear to share a common caffeine-producing evolutionary ancestor.

The team created a high-quality draft of the genome of Coffea canephora, a plant species that makes up 30 percent of the world’s coffee. The researchers then compared the genome to that of other species.

They found that coffee has larger numbers of genes related to alkaloid and flavonoid compounds compared to other plants like grape and tomato. These genes contribute to the bitterness and aroma of coffee beans. The coffee genome also showed a large number of N-methyltransferases which are involved in making caffeine.

When examining the caffeine enzymes, they found that these are more closely related to other genes within the coffee plant than the caffeine creating enzymes in tea or chocolate.

“The coffee genome helps us understand what’s exciting about coffee — other than that it wakes me up in the morning. By looking at which families of genes expanded in the plant, and the relationship between the genome structure of coffee and other species, we were able to learn about coffee’s independent pathway in evolution, including — excitingly — the story of caffeine,” said Victor Albert, professor of biological sciences at the University at Buffalo.

This finding demonstrates that caffeine is very valuable to plant species because coffee, tea and cocoa all developed the chemical independently. It is still not known, however, exactly what makes caffeine so essential to the plants. Some scientists have theorized that caffeine works as a insect repellant and helps to stunt the growth of resource competing plants. Others think that caffeine is addictive, which causes pollinators to return to and seek out the plants.

While this study doesn’t answer that question, understanding the evolutionary history of the plant may eventually lead to an understanding of when and why coffee developed caffeine and why the process of evolution selected that quality.