“The development of colour vision may have lead to Old World primates, and hence their human descendants, to lose their ability to detect pheromones, suggests a new genetic study. Pheromones are highly specific scent molecules that many animals rely upon to find and assess a potential mate.” The study establishes that the genetic emergence of full color vision in Old World primates coincided roughly with the shutoff of the pheromone signal transduction pathway, around 23 million years ago. How the switch to a visually-based approach to mate-selection conferred a selective advantage is a matter of speculation; it may relate to the ability to see color from a safer distance. New Scientist