“Is the human brain just a lot more of the same stuff, or has it changed in a qualitative way?”
The most likely similarity is the role of glucose in the regulation of gonadotropin releasing hormone (GnRH) secreting neurons of the mammalian brain. Food deprivation suppresses GnRH-dependent pulsatile luteinizing hormone (LH) secretion in rats, sheep, monkeys and humans, which is consistent with inhibition of pulsatile GnRH release.
GnRH, is the molecule Kochman (2012) indicated was perfectly constructed because it hasn’t changed during the past 400 million years, although diversification of its receptor appears to allow for things like pheromone-dependent self / non-self recognition (at the advent of sexual reproduction, which requires a primitive immune system and means for sexual orientation).
GnRH also links nutrient chemicals and pheromones directly to adaptive evolution via the required ecological, social, neurogenic, and cognitive niche construction evidenced by the apparent design in biology.