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This chapter examines the evolution of bird brain, social contact, and birdsong. Communicative capabilities are widespread, whether in song or through other forms of intimate social contact. One mechanism for this is the regulation of information molecules in the brain such as vasopressin and oxytocin. The chapter first provides an overview of information molecules before connecting these processes to song in frogs, crickets, and birds. It then considers neurogenesis and how information molecules work in the human brain, focusing on some core biology underlying animal song and social contact. It shows that steroid hormones facilitate neuropeptide expression in many species, which underlies song tied to the regulation of the internal milieu, territorial expression, reproduction, and a much wider range of social behaviors.

CRF is well known and studied as a hypothalamic-releasing factor. It, along with ACTH and cortisol, are mobilized under diverse conditions, including adversity, and are often thought of as part of the stress axis. CRF, however, is much more than this. One aim of this book is pushing the conception of CRF beyond the HPA axis, and what most people know about CRF. Since its original discovery, research has shown that this molecule is much broader than a hypothalamic-releasing factor. It took a while to discern CRF and its properties outside of its role as an ACTH-releasing factor. Now, the scientific community knows that CRF is a dynamic and diversely widespread peptide hormone with many roles and functions, beyond its role as a releasing factor in the brain. CRF in invertebrates is linked to basic regulatory functions such as osmotic regulation, food intake, learning, and circadian rhythmicity.

Chapter 2 begins with a depiction of the evolutionary origins of CRF in living things. CRF appears to date back hundreds of millions of years. It is found in diverse invertebrates, including flies and bees. Invertebrates’ brains look nothing like those of vertebrates except for the diverse information molecules that underlie both brain systems. There is no clear anatomical organ like the HPA axis in invertebrates, yet information molecules, including CRF, are just as important to invertebrate functioning as they are to vertebrates. CRF in invertebrates is linked to basic regulatory functions such as osmotic regulation, food intake, learning, and circadian rhythmicity. There are many examples of regulatory molecules that, over time, become adapted to serve multiple functions. Once a gene for a potent regulatory molecule exists, the potential for the differentiation of function, regulation, and mode of action exist as well.

Chapter 9 addresses what constitutes an information molecule, in general, and CRF, in particular. Our age is the age of information and CRF is now set in the larger context of the information age of the last 100 years. Thus, the conclusion summarizes the preceding chapters and looks at the large social context and the great range of scientific fields to promote a fuller understanding of this peptide, its structure, and its history. Our understanding of this one information molecule is expanding, as we learn more about its expression or overexpression beyond what is adaptive, as well as its moderation by other information molecules (e.g., GABA and oxytocin) and various contexts (e.g., species, age, gender, setting, or incentive). Information molecules cannot be looked at as independent entities, isolated from their context and other molecules, but rather in view of multiple factors that contribute to diverse outcomes.