Population genetics: an introduction for physicists

Abstract: Population genetics lies at the heart of evolutionary theory. This topic forms part of many biological science curricula but is rarely taught to physics students. Since physicists are becoming increasingly interested in biological evolution, we aim to provide a brief introduction to population genetics, written for physicists. We start with two background chapters: chapter 1 provides a brief historical introduction to the topic, while chapter 2 provides some essential biological background. We begin our main content with chapter 3 which discusses the key concepts behind Darwinian natural selection and Mendelian inheritance. Chapter 4 covers the basics of how variation is maintained in populations, while chapter 5 discusses mutation and selection. In chapter 6 we discuss stochastic effects in population genetics using the Wright-Fisher model as our example, and finally we offer concluding thoughts and references to excellent textbooks in chapter 7.

• The paper introduces interdisciplinary population genetics concepts tailored for physicists by merging evolutionary theory with statistical modeling.
• It explains essential mechanisms such as Mendelian inheritance, the Hardy-Weinberg equilibrium, and genetic drift using mathematical frameworks familiar to physicists.
• The study highlights the application of models like the Wright-Fisher model and coalescence theory to elucidate evolutionary dynamics and genetic variation.

Introduction to Population Genetics for Physicists: A Review

The paper, authored by Andrea Iglesias-Ramas, Samuele Pio Lipani, and Rosalind J. Allen, offers an introductory account of population genetics tailored for physicists. This effort stems from the increased interest among physicists in biological evolution. The document navigates through the foundational aspects of population genetics, bridging key biological concepts with theoretical perspectives that may resonate with statistical physics.

The authors embark on this academic journey with a succinct historical context, tracing foundational thoughts from Aristotle to modern evolutionary theory proponents. The text delineates how early static views of nature gave way to more dynamic propositions, eventually leading to contemporary understandings of biological evolution. The focus on Western academic developments sets the stage for introducing physicists to the biological lexicon necessary for grasping population genetics.

Subsequent sections provide essential biological background, explicating terminologies such as genes, alleles, genotypes, and phenotypes that are central to population genetic discourse. This is particularly beneficial for physicists who might not have deep familiarity with biological terminologies. The discussions on the central dogma of molecular biology provide a simplified yet sufficient framework for understanding how genetic information translates to phenotypic traits.

Further, the authors explore the intricacies of Mendelian inheritance and address the maintenance of variation in populations—a critical component of evolutionary processes. The text contrasts the concept of blending inheritance with that of Mendelian inheritance, drawing attention to how genetic variation is preserved through discrete inheritance mechanisms. The Hardy-Weinberg Principle is discussed as a cornerstone of population genetics, establishing equilibrium conditions under Mendelian inheritance.

The narrative continues by exploring mutation and selection, two pivotal forces in evolutionary dynamics. The authors describe fitness as a measure of an organism's reproductive success and emphasize the slow yet persistent impact of selection on genotype frequencies. Here, the discussion is mathematically grounded, aligning with the analytical practices familiar to a physics audience.

Stochastic effects, encapsulated under the term genetic drift, are examined through the Wright-Fisher model. This section highlights the role of genetic drift in allele frequency fluctuations due to random sampling effects, particularly in small populations. The authors further connect these stochastic effects to real-world genetic diversity scenarios, introducing concepts like heterozygosity and mutation-drift balance.

In advancing the neutral theory of molecular evolution, the paper synthesizes a stochastic view where genetic drift predominates at the molecular level. The simplification involving mutation-drift equilibrium is presented, underscoring neutral mutations’ role in genetic variance. This theory's coexistence with Darwinian natural selection offers a multifaceted understanding of evolutionary mechanisms.

Finally, the authors touch upon lineage coalescence, adopting a retrospective analysis of genetic data. By utilizing the Wright-Fisher model’s conceptual framework, they elucidate the probabilistic aspects of tracing ancestry, thereby facilitating discussions on the evolutionary history embedded in genomic sequences.

In conclusion, the paper serves as a scholarly primer on population genetics for physicists, aligning foundational biological concepts with theoretical models familiar to physicists. It sets the stage for interdisciplinary dialogues and potential research avenues where insights from physics could enrich the biological sciences. Future developments might see broader applications of computational models and statistical mechanics in unraveling the complexities of genetic evolution, fostering deeper collaboration between these traditionally distinct disciplines.