Club EvMed: Why is human childbirth so difficult? Obstetrics and the evolution of labor
Friday, June 11th at 12pm EDT/18:00 CEST
Join us for a conversation with Philipp Mitteroecker and Barbara Fischer, both in the Department of Evolutionary Biology’s Unit for Theoretical Biology at the University of Vienna, Austria. The incidence of obstructed labor in humans is strikingly high, in the range of 3-6% worldwide, mostly resulting from the disproportion of the mother’s pelvic dimensions and the newborn’s head. Mortality and morbidity due to this disproportion imposes a strong – and partly persisting – selection pressure. Why has natural selection not led to a wider female birth canal and reduced obstructed labor?
We present a model that explains the high rate of obstructed labor by the specific properties of the selection scenario involved in human childbirth. Drawing from epidemiology and evolutionary quantitative genetics, the model allows for an estimation of the strength of selection on neonatal and maternal dimensions. We show how moderate directional selection suffices to account for the high rates of cephalopelvic disproportion and discuss why selection is unable to reduce these rates. Furthermore, the model predicts a considerable evolutionary response of pelvic and/or neonatal dimensions resulting from the regular use of Caesarean sections, and it also explains the intergenerational “inheritance” of Caesarean delivery. We also show how environmental, economic, and demographic transitions contribute to the global rates of Caesarean section. This illustrates the importance of evolutionary theory to understand biosocial and epidemiological change in modern societies.
Attendees are encouraged to read Pavličev et al. 2020, “Evolution of the human pelvis and obstructed labor: New explanations of an old obstetrical dilemma” and Fischer et al. 2021, “Sex differences in the pelvis did not evolve de novo in modern humans.”
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Club EvMed: Evolution management from a game-theory perspective: can superbugs be forever tamed?
Monday, June 21st at 12pm EDT/18:00 CEST
When people “treat” a biological population, e.g., when a doctor prescribes an antibiotic, a farmer sprays an herbicide, or a homeowner mows their lawn, they create a selective pressure favoring organisms that can better survive and/or recover from treatment. It might therefore seem that rising resistance to treatment is inevitable. In this week’s conversation, Duke economics professor David McAdams will discuss why this is not necessarily the case—how the traditional logic of rising resistance hinges on an assumption of ignorance about the biological population. If the “evolution manager” has multiple treatment options and can observe the state of the population before deciding which treatment to prescribe, e.g., by conducting a rapid resistance diagnostic of an infecting pathogen or visually inspecting an unruly lawn, their subsequent informed treatment may then shape the fitness landscape in ways that serve human needs and, indeed, enhance the population’s future treatability. But there are important limitations, as the population may be impacted by the choices of other evolution managers (creating a “game” among managers) and some strategies with the potential to select against resistant organisms may only be feasible when resistance is sufficiently rare.
Attendees are encouraged to read McAdams et al. 2019, “Resistance diagnostics as a public health tool to combat antibiotic resistance: A model-based evaluation” and McAdams 2017, “Resistance diagnosis and the changing epidemiology of antibiotic resistance.”
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