Homo medicus: The transition to meat eating increased pathogen pressure and the use of pharmacological plants in Homo.

Bibliographic Collection: 
Publication Type: Journal Article
Authors: Hagen, Edward H; Blackwell, Aaron D; Lightner, Aaron D; Sullivan, Roger J
Year of Publication: 2023
Journal: Am J Biol Anthropol
Volume: 180
Issue: 4
Pagination: 589-617
Date Published: 2023 Apr
Publication Language: eng
ISSN: 2692-7691
Keywords: Animals, Brain, Hominidae, Humans, Mammals, Meat, Plants, Medicinal, Primates

The human lineage transitioned to a more carnivorous niche 2.6 mya and evolved a large body size and slower life history, which likely increased zoonotic pathogen pressure. Evidence for this increase includes increased zoonotic infections in modern hunter-gatherers and bushmeat hunters, exceptionally low stomach pH compared to other primates, and divergence in immune-related genes. These all point to change, and probably intensification, in the infectious disease environment of Homo compared to earlier hominins and other apes. At the same time, the brain, an organ in which immune responses are constrained, began to triple in size. We propose that the combination of increased zoonotic pathogen pressure and the challenges of defending a large brain and body from pathogens in a long-lived mammal, selected for intensification of the plant-based self-medication strategies already in place in apes and other primates. In support, there is evidence of medicinal plant use by hominins in the middle Paleolithic, and all cultures today have sophisticated, plant-based medical systems, add spices to food, and regularly consume psychoactive plant substances that are harmful to helminths and other pathogens. We propose that the computational challenges of discovering effective plant-based treatments, the consequent ability to consume more energy-rich animal foods, and the reduced reliance on energetically-costly immune responses helped select for increased cognitive abilities and unique exchange relationships in Homo. In the story of human evolution, which has long emphasized hunting skills, medical skills had an equal role to play.

DOI: 10.1002/ajpa.24718
Alternate Journal: Am J Biol Anthropol