Question

For decades, paleoanthropological models of human encephalization relied on the 'expensive tissue hypothesis,' which posited a strict evolutionary constraint: because brain tissue imposes exceptionally high basal metabolic demands, the expansion of the hominin brain was possible only through a commensurate reduction in the mass of another metabolically costly organ system, specifically the gastrointestinal tract. Proponents argued that this visceral contraction was facilitated by adopting an energy-dense diet of cooked tubers and animal protein.

However, recent broad-scale comparative mammalian analyses have called this supposed anatomical trade-off into question. When researchers controlled for fat-free body mass across over one hundred mammalian taxa, the inverse correlation between brain mass and digestive tract volume dissolved completely. Instead, evolutionary biologists now emphasize that metabolic adaptations are multifaceted: rather than relying on a solitary organ-for-organ trade-off, hominins sustained encephalization through an ensemble of energetic strategies. Notably, studies comparing primates with humans reveal that basal metabolic stability was underwritten by the evolution of expanded subcutaneous adipose reserves. In this framework, the metabolic costs associated with hepatic gluconeogenesis during periods of nutritional scarcity are significantly mitigated in adipose-rich hominins, preventing the catabolic degradation of neural tissue without necessitating permanent visceral shrinkage.

In the context of the passage, the author's reference to 'the metabolic costs associated with hepatic gluconeogenesis' serves primarily to do which of the following?