Lessons from naked apes and their infections

Area of Science:

• Evolutionary biology
• Infectious diseases
• Human origins

Background:

• Human infections originate from two primary sources: vertically transmitted 'family heirlooms' co-evolved with hosts and horizontally transmitted 'new acquisitions' from cross-species infections.
• Humans, or 'naked apes', possess a broader spectrum of pathogens than other apes, acquiring them from domesticated, commensal, and exotic species sharing our environment.

Purpose of the Study:

• To review the diversity of human infections, particularly retroviruses, in the context of human evolution.
• To explore the evolutionary origins of human ectoparasites, such as lice, in relation to human nakedness and ape lice.
• To investigate the potential for pathogen exchange between humans and extinct hominid species.

Main Methods:

• Comparative analysis of pathogen reservoirs in humans and other primates.
• Review of existing literature on human infectious diseases, retroviruses, and parasite evolution.
• Phylogenetic and evolutionary inference regarding pathogen transmission routes.

Main Results:

• Humans harbor a uniquely diverse collection of pathogens ('metagenome') compared to other apes.
• Human nakedness presents unique evolutionary pressures on ectoparasites, influencing the origin and evolution of human lice from ape lice.
• Evidence suggests potential horizontal pathogen transmission between humans and other hominid species.

Conclusions:

• Human infectious disease profiles are shaped by both ancient co-evolutionary relationships and recent cross-species transmissions.
• The evolution of human lice is intrinsically linked to the evolutionary trajectory of human skin and hairlessness.
• Further research into pathogen exchange with extinct hominids could illuminate human evolutionary history and disease emergence.