Evolutionary demographic models for mortality plateaus

Area of Science:

• Evolutionary biology
• Demography
• Mathematical modeling

Background:

• Observed mortality plateaus at extreme ages in diverse species (medflies, Drosophila, nematodes, humans).
• Mueller and Rose's age-structured demographic models propose evolutionary mechanisms (mutation accumulation, antagonistic pleiotropy) predicting late-life mortality plateaus.

Purpose of the Study:

• To define a class of Markovian models encompassing Mueller and Rose's models.
• To characterize the limiting states of these demographic models.
• To investigate the theoretical underpinnings of observed late-life mortality patterns.

Main Methods:

• Definition of a class of Markovian age-structured demographic models.
• Analysis of model properties, focusing on limiting states.
• Comparison of model predictions with empirical observations of mortality plateaus.

Main Results:

• For the basic model, mortality plateaus above a minimal threshold are not limiting states.
• The proposed models, in their basic form, do not fully explain persistent mortality plateaus as limiting states.
• Transient states within the models do exhibit mortality plateaus.

Conclusions:

• The theoretical models of Mueller and Rose, while influential, do not predict late-life mortality plateaus as stable limiting states.
• The failure of the basic model is not due to previously conjectured reasons.
• Further exploration of related models may reconcile evolutionary theory with observed mortality patterns in aging populations.