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Date of Award
Spring 2024
Document Type
Masters Thesis
Department or Program Affiliation
Anthropology
Degree Name
Master of Arts (MA)
Department
Anthropology
First Advisor
Monson, Tesla A.
Second Advisor
Schwandt, Hilary M.
Third Advisor
Koetje, Todd A.
Abstract
Litter size plays an important role in the life history strategies of all mammalian taxa. It is one of the most important factors determining whether an organism is deemed to have a ‘slow’ or ‘fast’ life history strategy. Investigating how the evolution of litter size has influenced human evolution, extant primate biodiversity, and how it relates to other life history traits is crucial to understanding ourselves and our closest relatives. This thesis summarizes a two-pronged investigation into the evolution of litter size: 1) I performed a meta-analysis using 955 taxa within the magnorder Boreoeutheria, and 2) I performed a geometric morphometric pilot study on twinning and singleton-bearing American monkey (Platyrrhini) crania. My findings include negative correlations between litter size and gestation length, age at maturation, and maximum potential lifespan. Phylogenetic signal tests support that selection has played a role in the distribution of mean litter size across this magnorder, as well as in the distribution of other reproductive characters including gestation length and percentage of brain growth accomplished prenatally. Additionally, I present reconstructions of life history and body size for various ancestral organisms within this magnorder. My results support that twinning was common in boreoeutherian evolution and may have been the ancestral primate condition. To better evaluate these results, I compare the reconstructed values for the ancestral boreoeutherian to recent morphology-informed research on fossil mammals including Vincelestes neuguenianus (Theria). Finally, I present the results of the pilot study, discuss how these relate to my current hypothesis regarding litter size and morphological covariation, and discuss how I intend to expand this dataset.
Type
Text
Keywords
Litter, primatology, phylogenetics, morphology, encephalization, evolution, reconstruction
Publisher
Western Washington University
OCLC Number
1438570632
Subject – LCSH
Primates--Evolution; Primates--Phylogeny; Primates--Life cycles; Primates--Morphology; Primates--Reproduction; Primatology; Evolution (Biology)
Format
application/pdf
Genre/Form
masters theses
Language
English
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.
Recommended Citation
McBride, Jack Hansen, "The Evolutionary History of Primate Litter Size" (2024). WWU Graduate School Collection. 1298.
https://cedar.wwu.edu/wwuet/1298
Descriptive Data
Table S2. Phylogenetic Signal.docx (15 kB)
Phylogenetic Signal Results
Table S3. PGLS.docx (19 kB)
Phylogenetic Generalized Least Square Results
Table S4. Full Dataset.csv (516 kB)
Full Dataset
Table S5. Full References for Dataset.docx (24 kB)
Refs for Dataset
Table S6. Complete.pdf (6201 kB)
Ancestral State Reconstruction
Table S6.5. Node Values.xlsx (318 kB)
Ancestral State Reconstruction Node Values