For my previous career as mathematical biologist: "The Ecological Detective" by Hilborn and Mangel, and "Introduction to Quantitative Genetics" by Falconer and Mackay. The first is a fascinating, exciting, and readable journey into biology, statistics, and thinking like a detective (data, models, theory, and how much weight one should assign to each component of the investigation), which is how people doing biological research should think. The second is a very readable introduction to Quantitative Genetics, which comprises the mathematical and statistical tools we should use when we talk about selection, drift, and heritability of traits.
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