Modern theories of human evolution converge on the belief that our brain has been designed to cope with problems that occurred intermittently in our evolutionary past. Evidence suggests that, during over 99 percent of the evolutionary process leading to the emergence of our species, our ancestors communicated in a synchronous and colocated manner, and employing facial expressions, body language, and oral speech (what we refer to here, generally, as ìface-to-faceî communication). Thus, it is plausible to assume that many of the evolutionary adaptations our brain has undergone in connection with communication have been directed at improving the efficiency and effectiveness of face-to-face communication, which begs the question: What happens when we selectively suppress face-to-face communication elements (e.g., colocation, the ability to employ/observe facial expressions) through e-communication technologies? This paper tries to provide an answer to this question by developing a hypothesis, called the media naturalness hypothesis, which builds on modern human evolution theory. The media naturalness hypothesis argues that, other things being equal, a decrease in the degree of naturalness of a communication medium (or its degree of similarity to the face-to-face medium) leads to the following effects in connection with a communication interaction: (1) increased cognitive effort, (2) increased communication ambiguity, and (3) decreased physiological arousal. It is argued that the media naturalness hypothesis has important implications for the selection, use, and deployment of e-com- munication tools in organizations, particularly in the context of business-to-consumer interactions.