What is the caffeine content of different coffee beans?

The caffeine content in coffee is not merely a matter of roast profile or brewing method; it is an evolutionary adaptation. Robusta, native to lower-altitude, tropical environments, evolved higher caffeine levels as a chemical deterrent against pests and diseases. This bitterness is a functional trait for the plant, not just a flavor profile for the consumer. Conversely, Arabica, which thrives at higher altitudes with lower pest pressure, requires less chemical defense, resulting in a more delicate, sugar-rich bean. A common misconception is that dark roasts contain significantly less caffeine than light roasts due to 'burning off' the stimulant. In reality, while roasting does cause some mass loss and moisture evaporation—which can slightly concentrate caffeine by weight—the change is marginal compared to the inherent genetic difference between species. For the producer, this means Robusta is often a more resilient, higher-yielding crop, but its aggressive chemical profile requires careful processing to mitigate the harsh, astringent notes that accompany its high caffeine density. When you choose a coffee, you are choosing a specific evolutionary strategy: the high-octane, defensive chemistry of Robusta or the refined, sugar-forward profile of high-altitude Arabica.