Science 1 June 2012:
Vol. 336 no. 6085 pp. 1154-1157
Across vertebrates, behaviorally relevant brain regions are remarkably conserved over 450 million years of evolution.
Simply put, the nutrients that organisms eat are metabolized to the pheromones they produce, which control social decision-making in all species. This article (linked above) is concise and somewhat parallels what I published as a 57-page journal article in the Journal of Psychology and Human Sexuality, and as a book chapter in the Handbook of the Evolution of Human Sexuality.
Excerpt (not simply put): “The overall influence of mammalian olfactory/pheromonal input on hypothalamic GnRH release and on LH release from the pituitary represent a highly conserved effector system that includes genes that code for the peptide ligand (i.e., GnRH) and the cell-surface receptor: the GnRH receptor (GnRHR). The result of this genetic conservation of GnRH and its receptor is the physiological regulation of sexual reproduction across species. The transition from asexual to sexual reproduction involves two organisms that incorporate the equally well-conserved GnRH-directed, GnRHR-enabled neuroendocrine system signaling mechanism and the MHC/HLA-directed immune system signaling mechanism. These signaling mechanisms are involved in the chemical discrimination of self from non-self, genetic diversification, and the neuroendocrine response to non-self chemical signals, like olfactory/pheromonal input from the social environment.”
Clearly, it is the GnRH neuronal system that is the evolved vertebrate social decision-making network.
How could the cause of our social decision-making not be the adaptive evolution from yeasts of the ligand-receptor binding exemplified across species by the conservation of gonadotropin releasing hormone (GnRH) and diversification of its receptor (GnRHR) as detailed in Kohl (2006/7)? Model organisms like the threespine stickleback make clear the involvement of ecological niche construction. The honeybee is the invertebrate model organism that makes clear the involvement of the nutrient dependent ecological niche in construction of the pheromone-dependent social niche. Invertebrate and vertebrate models collectively attest to the common molecular biology of adaptively evolved social decision-making networks.
In mammals, the hypothalamic neurogenic niche (e.g., probably located in the medial preoptic area) responds to nutrients to enable fertility and responds to pheromones that enable sexual reproduction, which has adaptively evolved from its origins in brewer’s yeast. Never before has there been such a clear representation of cause and effect across species from microbes to man, where nutrient chemicals calibrate the intracellular signaling and their metabolism to pheromones standardizes and controls the stochastic gene expression required for reproduction.
RNA-mediated gene expression enables adaptive evolution of the brain and ensures that our ability to acquire nutrient chemicals is the first priority for reproduction via appropriate social behaviors, as it is in every species. For example, microbes eat the DNA of heterospecifics but not conspecifics, which indicate more social sense than what some people today are capable of recognizing in the design of biology (e.g., the evolved gene, cell, tissue, organ, organ system pathway that directly links sensory input to the mammalian neuroendocrine system and the hormones responsible for our behavior, which activates the same ‘organized’ pathway). The reciprocity of organization and activation is required for adaptive evolution that is driven by nutrient chemicals and pheromones.