FROM THE MAY 2013 ISSUE of Discover
Grandma’s Experiences Leave a Mark on Your Genes
Your ancestors’ lousy childhoods or excellent adventures might change your personality, bequeathing anxiety or resilience by altering the epigenetic expressions of genes in the brain.
By Dan Hurley|Tuesday, April 23, 2013
Excerpt: “A study from Randy Jirtle of Duke University showed that when female mice are fed a diet rich in methyl groups, the fur pigment of subsequent offspring is permanently altered. Without any change to DNA at all, methyl groups could be added or subtracted, and the changes were inherited much like a mutation in a gene.”
My comment: Studies on invertebrates and vertebrates have since shown that adaptive evolution is nutrient-dependent and pheromone-controlled. This links the epigenetic effects of food odors and their metabolism to species specific pheromones to ecological, social, neurogenic, and socio-cognitive niche construction via the molecular mechanisms common to species from microbes to man. The honeybee model organism is one of the best for showing cause and effect. What the queen eats determines her pheromone production and everything involved in the interactions in the colony, including the neuroanatomy of the worker bees’ brains.
Bottom up (nutrient-dependent) and top down (pheromone-control of reproduction) epigenetic effects eliminate from further consideration any theory that posits mutational cause of adaptively evolved phenotypes. Variations are nutrient-dependent and pheromone-controlled, not caused by mutations and runaway selection (–as in selection for what?)
Excerpt: “…natural variations in the amount of licking and grooming received during infancy had a direct effect on how stress hormones, including corticosterone, were expressed in adulthood.”
My comment: The epigentic effect on stress hormones is due to the association of tactile stimulation with nutrient-dependent pheromone-controlled changes in gonadotropin releasing hormone (GnRH) pulse frequency, which alters levels of other hormones during the development of the brain and behavior in mammals. Cause and effect is olfactory/pheromonal, not tactile. There is no direct effect of tactile stimulation on gene activation in GnRH neurosecretory neurons of the brain. That direct effect is required to link sensory input to differences in development of the brain and to affects on behavior. See for details:
Nutrient-dependent / Pheromone-controlled Adaptive Evolution
Nutrient-dependent / Pheromone-controlled thermodynamics and thermoregulation
