The present review assesses the phylogenetic history of information molecules (bioregulators pheromones, hormones, neuroactive compounds), receptors, transducers, second messengers) in uni- and multicellular organisms. Transitional stages between contemporary endocrine secretions including hormones and neuroactive materials, and primogenial exocrine compounds (pheromones) are proposed. Severalhypotheses have been developed to explain the origin and evolution of bioregulator/receptor units. Finally, how these primordial information molecules have either been co-opted or have changed their function during the course of biological evolution is analysed.

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