Biomedical
DHEAS and Human Development: An Evolutionary Perspective
Abstract
Adrenarche, the post-natal rise of DHEA and DHEAS, is unique to humans and the African Apes. Recent findings have linked DHEA in humans to the development of the left dorsolateral prefrontal cortex (LDPFC) between the ages of 4–8 years and the right temporoparietal junction (rTPJ) from 7 to 12 years of age. Given the association of the LDLPFC with the 5-to-8 transition and the rTPJ with mentalizing during middle childhood DHEA may have played an important role in the evolution of the human brain. I argue that increasing protein in the diet over the course of human evolution not only increased levels of DHEAS, but linked meat consumption with brain development during the important 5- to-8 transition. Consumption of animal protein has been associated with IGF-1, implicated in the development of the adrenal zona reticularis (ZR), the site of DHEAS production. In humans and chimps, the zona reticularis emerges at 3–4 years, along with the onset of DHEA/S production. For chimps this coincides with weaning and peak synaptogenesis. Among humans, weaning is completed around 2 ½ years, while synaptogenesis peaks around 5 years. Thus, in chimpanzees, early cortical maturation is tied to the mother; in humans it may be associated with post-weaning provisioning by others. I call for further research on adrenarche among the African apes as a critical comparison to humans. I also suggest research in subsistence populations to establish the role of nutrition and energetics in the timing of adrenarche and the onset of middle childhood.
Key Questions
What is DHEAS, and what role does it play in human development?
Dehydroepiandrosterone sulfate (DHEAS) is a steroid hormone produced by the adrenal glands. It serves as a precursor to sex hormones and has been linked to various developmental processes, including brain maturation. Elevated DHEAS levels during childhood are associated with the development of specific brain regions, such as the left dorsolateral prefrontal cortex (LDPFC) and the right temporoparietal junction (rTPJ).
How does DHEAS influence brain development in humans?
DHEAS has been linked to the development of the LDPFC between the ages of 4–8 years and the rTPJ from 7 to 12 years of age. The LDPFC is associated with cognitive skills that allow for greater individual independence, while the rTPJ is involved in mentalizing during middle childhood. These associations suggest that DHEAS may have played an important role in the evolution of the human brain.
What is adrenarche, and how is it related to DHEAS production?
Adrenarche is the post-natal rise of DHEA and DHEAS, unique to humans and African apes. In humans, the zona reticularis, the site of DHEAS production, emerges at 3–4 years, coinciding with the onset of DHEA/S production. This period aligns with weaning and peak synaptogenesis in chimpanzees, while in humans, weaning is completed around 2½ years, and synaptogenesis peaks around 5 years.
How does DHEAS production differ between humans and chimpanzees?
In chimpanzees, early cortical maturation is tied to the mother, whereas in humans, it may be associated with post-weaning provisioning by others. This difference suggests that the pattern of DHEAS production during this period differs between humans and chimpanzees, primarily by magnitude or timing.
What implications do these findings have for understanding human evolution?
The association of DHEAS with brain development during critical periods suggests that increasing protein in the diet over the course of human evolution not only increased levels of DHEAS but also linked meat consumption with brain development during the important 5-to-8 transition. This dietary shift may have contributed to the unique aspects of human brain maturation and cognitive abilities.
