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Pages
Posts
publications
Genotype-by-environment interactions modulate the rate of microevolution in reproductive timing in humans Permalink
Published in Evolution, 2022
A trait can be heritable and under consistent directional selection and still evolve at a rate that varies over time. This paper shows how genotype-by-environment interactions produce exactly that outcome in human reproductive timing.
Recommended citation: Mawass, W., Mayer, F. M., and Milot, E. (2022). "Genotype-by-environment interactions modulate the rate of microevolution in reproductive timing in humans." Evolution, 76(7), 1391–1405.
Assessing the impact of pedigree attributes on the validity of quantitative genetic parameter estimates Permalink
Published in Journal of Evolutionary Biology, 2025
Quantitative genetic inference from historical genealogies rests on pedigrees that were never designed for the purpose. This paper asks how their depth, completeness, and structure shape the parameter estimates we draw from them.
Recommended citation: Mawass, W., and Milot, E. (2025). "Assessing the impact of pedigree attributes on the validity of quantitative genetic parameter estimates." Journal of Evolutionary Biology, 38(4), 439–456.
Contrasting evolutionary outcomes in a human life history trait which is heritable and under consistent unbiased directional selection Permalink
Published in bioRxiv, 2025
If selection is consistent and the trait is heritable, replicate populations should evolve along similar trajectories. They do not. This preprint tests the consistency of evolutionary outcomes across replicate human populations.
Recommended citation: Mawass, W., and Milot, E. (2025). "Contrasting evolutionary outcomes in a human life history trait which is heritable and under consistent unbiased directional selection." bioRxiv, 2025.10.13.682154.
Quantifying the susceptibility of polygenic scores to ancestry stratification Permalink
Published in bioRxiv, 2025
Polygenic scores inherit whatever population structure the underlying GWAS failed to control. This preprint quantifies how susceptible they are, and what residual stratification does to downstream inference.
Recommended citation: Blanc, J., Mawass, W., and Berg, J. J. (2025). "Quantifying the susceptibility of polygenic scores to ancestry stratification." bioRxiv, 2025.12.04.692430.
Extinction vortices are driven more by a shortage of beneficial mutations than by deleterious mutation accumulation Permalink
Published in Proceedings of the Royal Society B, 2026
Small populations are usually thought to spiral toward extinction because deleterious mutations accumulate. We show that the shortage of beneficial mutations — mutational drought — is the stronger driver over long timescales.
Recommended citation: Mawass, W., Hernández, U., Matheson, J., Berg, J. J., and Masel, J. (2026). "Extinction vortices are driven more by a shortage of beneficial mutations than by deleterious mutation accumulation." Proceedings of the Royal Society B, 293(2072), 20260600.
High deleterious mutation rate distorts site frequency spectrum in mammals and leads to erroneous inference of demographic expansions
In preparation
Demographic inference assumes the neutral site frequency spectrum is shaped by demography. In mammals, a high deleterious mutation rate distorts it enough to manufacture expansions that never happened.
Information about the derived orientation of disease risk-increasing variants provides power to detect signals of directional selection on diseases
In preparation
Knowing which allele is derived, not merely which raises risk, adds statistical power to tests for directional selection on disease traits.
Measured fitness variance is too weak to explain the missing diversity
In preparation — advanced manuscript available upon request
Published heritable fitness variances from 19 vertebrate populations are too small to explain observed diversity deficits, and at the same time too large to be maintained at equilibrium.
Linked neutral diversity under stabilizing selection: a two-locus moments model
In preparation
A two-locus moments framework for how stabilizing selection shapes diversity at linked neutral sites.
Evaluating bias in polygenic score associations due to imperfect control of population stratification
In preparation — advanced manuscript available upon request
A random matrix theory treatment of what principal component correction can and cannot remove, and how the residual propagates into polygenic score associations.
Rare variants drive high variance in human ancestral fitness at mutation-selection-drift balance Permalink
Published in bioRxiv, 2026
At mutation-selection-drift balance, most of the variance in ancestral fitness traces to rare variants rather than common ones.
Recommended citation: Hernández, U., Mawass, W., Matheson, J., and Masel, J. (2026). "Rare variants drive high variance in human ancestral fitness at mutation-selection-drift balance." bioRxiv, 2026.07.29.741368.
research
Evolutionary predictability in human populations
Deep genealogical records let us watch selection act on human life-history traits over centuries. What they show is that heritability plus selection does not predict the outcome.
Linked selection and the neutral diversity we actually observe
Published heritable fitness variances are too small to explain the diversity wild populations have lost, and too large to be maintained at equilibrium. No rescaling of the estimates resolves both at once.
Mutational drought and the fate of small populations
Small populations are usually thought to decline because deleterious mutations accumulate. The shortage of beneficial mutations turns out to matter more.
Population stratification and the limits of polygenic inference
How much population structure survives standard correction in large biobanks, and what the residual does to polygenic scores and tests for selection.
talks
teaching
GNT 1007 — Molecular Genetics
Guest Lecturer, Université du Québec à Trois-Rivières, 2019
Delivered interactive lectures to undergraduate biology majors on quantitative trait inheritance, gene-environment interactions, and variance partitioning approaches. Spring 2019.
ECOL 419/519 — Introduction to Modeling in Biology
Preceptor, undergraduate and graduate course, University of Arizona, Ecology and Evolutionary Biology, 2021
Taught upper-level undergraduate and graduate students mathematical modeling, computational simulation methods, and how to read and interrogate scientific literature, working in R, Python, and Mathematica. Spring 2021.
ECOL 599 — Independent Study on Theoretical and Empirical Population Genetics
Co-Lead Instructor, graduate seminar, University of Arizona, Ecology and Evolutionary Biology, 2021
Co-designed the syllabus and led weekly discussion-based seminars on foundational and contemporary population genetics literature, spanning the theoretical and the empirical. 2021–2023.