Researchers who've sequenced the genome of coffee say they've learned a lot about how it came to create caffeine, everybody's early morning buzz friend.

Caffeine is found in coffee, tea and chocolate, but scientists say the position and sequences of the genes involved in producing caffeine in coffee suggests they evolved independently of the genes in chocolate and tea that serve the same function.

That shows coffee did not inherit the caffeine-linked genes from a shared common ancestor of the three plants but rather evolved them on its own, they say.

The first sequencing of the coffee genome was conducted on the robusta coffee plant, a variety accounting for around a third of the 2.5 billion cups of coffee consumed around the world daily.

"The coffee genome helps us understand what's exciting about coffee -- other than that it wakes me up in the morning," says Victor Albert of the University of Buffalo, one of the authors of the published study.

"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."

Although caffeine is the attraction of coffee for most people, it's unclear why the coffee plant would have evolved it, the researchers say.

Theories range from deterring leaf-eating insects to making surrounding soil inhospitable to competing plant species to encouraging pollinators by making them wide-awake caffeine addicts.

All three theories may be accurate at least in part, Albert says.

Still, he says, caffeine is obviously important enough to have evolved independently in coffee, tea and chocolate, he says.

Their last shared common ancestor was more than 100 million years ago.

"So we're talking about plants that have been separated for a very long time that have independently evolved the capacity to make caffeine," Albert says.

One benefit of the newly sequenced coffee genome is the possibility of using the finding to improve breeding practices and even engineer new varieties of coffee, he notes.

Or even wind the clock back on caffeine for those who aren't that fond of it, Albert suggests.

"[Genetic engineering] might make it possible to knock off caffeine production in a variety of coffee plant," he says. "So to make decaf coffee, you wouldn't have to go through the process of extracting the caffeine. You could just grow coffee beans that don't make it at all."