The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

The timescale and evolutionary dynamics of Mycobacterium tuberculosis infection in humans


1Center for Infectious Disease Dynamics, The Pennsylvania State University, 2Division of Infectious Diseases, Stanford University

Friday 5:45-6:00, Parlors Add to calendar

The human bacterial pathogen Mycobacterium tuberculosis (MTB) is the causative agent of tuberculosis and is one of the leading single-agent causes of global infectious disease mortality, second only to HIV/AIDS. MTB is found throughout the globe and may infect as many as one-in-three individuals, which combined suggest a long evolutionary history of infection in humans. Indeed, prevailing hypotheses suggest that humans acquired this important pathogen prior to their out-of-Africa expansion more than 40,000 years ago, and that subsequent ancient human migrations are responsible for the present geographic distribution of M. tuberculosis. However, most evidence supporting the antiquity of MTB is indirect., and in the absence of direct evidence from the bacterium itself, it is unclear how assumptions about the antiquity of MTB may color our interpretation of existing evidence.

Interestingly, recent work in indigenous North American populations indicates that MTB accumulates diversity over short timescales and that previous assumptions about the low rate of MTB evolution must be re-examined. Herein, we analyze a large, novel data set of full MTB genome sequences to reveal and link the evolutionary dynamics of this critical human pathogen with human population history. Importantly, we estimate that the tempo of MTB evolution to be as much as two orders of magnitude faster than previously assumed. Critically, our estimates suggest that the most recent common ancestor of MTB existed as recently as several millennia ago, and that more recent shifts in human behavior are likely to explain the observed distribution of this potent human pathogen today.

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