The Buzz in Your Coffee is the Result of Millions of Years of Plant Evolution

Carl Zimmer writes at NYT:

Caffeine may be a drug, but it’s not the product of some underworld chemistry lab; rather, it’s the result of millions of years of plant evolution...

The evolution of caffeine in coffee started when the gene for an N-methyltransferase mutated, changing how the enzyme behaved. Later, the plants accidentally duplicated the mutated gene, creating new copies. Those copies then mutated into still other forms.

“They’re all descendants of a common ancestor enzyme that started screwing around with xanthosine compounds,” said Victor A. Albert, an evolutionary biologist at the University at Buffalo and co-author of the new study...

When coffee leaves die and fall to the ground, they contaminate the soil with caffeine, which makes it difficult for other plants to germinate. Coffee may thus use caffeine to kill off the competition.

Coffee plants also use caffeine to ward off insects that would otherwise feast on their leaves and beans. At high doses, caffeine can be toxic to insects. As a result, insects have evolved taste receptors that help them avoid ingesting caffeine.

But coffee and a number of other plants also lace their nectar with low doses of caffeine, and in that form, it seems to benefit the plants in a different way.

Plants make nectar to feed insects and other animals so they’ll spread their pollen. When insects feed on caffeine-spiked nectar, they get a beneficial buzz: they become much more likely to remember the scent of the flower. This enhanced memory may make it more likely that the insect will revisit the flower and spread its pollen further.

“It’s a very cool fact that you can use one molecule to do a negative thing and a positive one,” said Julie A. Mustard, a neurobiologist at the University of Texas at Brownsville.

It may be a coincidence of biology that caffeine-producing plants have a similar effect on us—toxic at high doses but enhancing our brains at low doses. “They’re manipulating all of us,” Dr. Mustard said.