Abstract

Reproductive senescence is often tied to organismal senescence, that is, an organism’s reproductive output continues throughout the lifespan and only ends when an organism reaches the end of its life. In some species, reproductive senescence occurs before organismal senescence, known as the post-reproductive lifespan (PRLS). Some species have an adaptive PRLS, meaning that this trait is present across multiple populations and that they receive a fitness benefit over those that do not have a PRLS. Species known to have an adaptive PRLS include humans (Homo sapiens), orcas (Orcinus orca), short-finned pilot whales (Globicephala macrorhynchus), and potentially Asian elephants (Elephas maximus). The physiological processes and evolutionary pressures that led to the appearance and persistence of adaptive PRLSs are understudied. In this paper, I review current literature on ovarian cycles and reproductive aging in vertebrates, as well as literature on the hypotheses for the appearance of adaptive PRLSs to answer two main questions: 1) Why is the adaptive PRLS seemingly so rare? and 2) What other species potentially have an adaptive PRLS? My research suggests that PRLSs are rare because the ecological conditions that favor them are rare, and that adaptive PRLSs may be found in some primates, most odontocetes, and some species of bird and fish.

Advisor

Lynn, Sharon

Department

Biology

Disciplines

Behavior and Ethology | Biodiversity | Biology | Comparative and Evolutionary Physiology | Ecology and Evolutionary Biology | Evolution | Organismal Biological Physiology | Physiology

Keywords

Menopause, Post-reproductive Lifespan, Ovarian cycles, Evolution, Killer Whales, Orcas, Asian Elephants, Elephants, Pilot Whale, Adaptive Post-reproductive Lifespan

Publication Date

2025

Degree Granted

Bachelor of Arts

Document Type

Senior Independent Study Thesis

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Available for download on Monday, July 22, 2030

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© Copyright 2025 Joe Carter