Thoughts on reading the Introduction to “The Structure and Confirmation of Evolutionary Theory” by Elisabeth A. Lloyd

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Lloyd describes J. J. C. Smart’s opinion that biologists use statistics only to do significance testing on experimental data and not to extract trends and create generalizable models of underlying fundamental processes as scientists in other disciplines (notably physics and chemistry) do.

In my experience of learning statistics and talking with others about statistics, this is not an entirely unfair accusation. The only statistics I learned during my undergraduate studies in biology were related to basic significance testing (e.g. t-tests and chi-squared tests) and how to formulate hypotheses testable by these methods. It wasn’t until after completing my masters degree that I have started to learn in depth, through self-motivated study, about linear modeling, how that relates to principles of experimental design and power analysis, and how to generalize responsibly. Continue reading

How fast is evolution?

This question came up during a class I took during my masters studies at the ETH Zurich. What is the maximum speed of evolution? On what factors does it depend? We discussed the idea that selection curbs the speed of evolution, acting as a brake by removing some phenotypes from the population and preventing evolution from continuing down those trajectories.

In that case, evolution without brakes means evolution in the absence of selection. All individuals reproduce in a statistically equal way, and individuals carrying mutations that in the real world would be lethal have just as many offspring as anyone else.

If we think of evolution in terms of travel through sequence space, then we can ask what affects the speed of that travel. Imagine that we start with a single reproducing genotype GREENĀ of length K in an environment that imposes no restrictions on population size or anything else.

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