Draft skeleton. Stage scenarios and anchor quotes are in place; the simulator and code panels are not yet wired. This is the most speculative lesson in the course.
Physics is the study of physical matter and how it changes over time. Evolution, at its fundamental core, is the study of information and how it changes over time. Because information is inherently heritable. The processes by which information changes over time are selection, drift, vertical versus horizontal transmission, and the generation of novel variants. The mechanism doesn't matter — DNA, prion folding, language, money, last names, viral RNA. The thing that's evolving is information.
— 202_lec31_01
A — Strip the substrate away
Drop the assumption that the replicators are DNA. Build a Price-equation engine that just needs heritability, variation, and differential reproduction. Prions, memes, language — they all evolve. The math doesn't care.
Prions are folded proteins. They encounter other proteins, fold them into the same shape. The new folded protein goes out and folds others into replicas of itself. Ones that fold more quickly become more common. Ones that fold with higher fidelity become more common. They make copies of themselves. No DNA involved. No mutations involved in the genetic sense. So the definition of "copying yourself" can't be DNA-centric.
— 202_lec30_02
TODO: substrate-agnostic Price-equation engine. Inputs: a trait z, a fitness w(z), an inheritance map. Outputs: cov(w, z) and Δz̄. Run on a prion sim, on a meme-spread sim, on a language-shift sim.
B — Memes are heritable ideas
Dawkins coined the word "meme" in 1976. In the original sense it just meant a heritable idea. Some spread; some don't. The math of frequency change is the same population genetics — just with a much higher mutation rate. Run a meme-spread sim.
The word "meme" was invented by evolutionary biologists in the 1970s. To discuss the fact that ideas are heritable. Some spread through a population more than others. The generic word for a heritable nucleotide-based unit was "gene." A "meme" was an idea that did the same thing. In the modern internet age it refers to things that are funny — but the concept was always broader. Newton's law of gravity is a meme. Darwin's theory of natural selection is a meme. Religions are memes. Anything passed from one mind to another, with variation and differential replication, evolves the same way a gene does. It's just the math. The numbers are different. The mutation rate is way higher.
— 461_lec21_03
TODO: meme-spread sim. Population of agents; idea variants with fidelity-of-transmission slider; trajectory of variant frequencies. Compare to allele-frequency math.
C — Holobionts — is the host+microbiome a unit?
Your microbiome is a community of microorganisms that affects your fitness. Is the host+microbiome a single selection unit? Run the Price decomposition. The diagnostic answers: when does the holobiont win out over the host alone? The answer is debated and the diagnostic gives the framework, not the verdict.
Aliens on another planet — are they going to use nucleotides? Almost certainly not. If they do, it won't be in the same sequences. But they'll still have heredity. So what does heredity mean in that sense? What are you passing on? It can't be DNA-centric. The same population genetics math worked out before we knew about DNA, so the math is more general than the application. The thing being inherited is information.
— 202_lec31_02
TODO: holobiont Price ratio. cov(W_holobiont, Z_holobiont) on a holobiont trait (e.g., immune profile) vs within-holobiont cov on microbe alleles. Show the cases where the holobiont is and isn't the unit.
D — Pick your own candidate
Free-response stage. The student picks a system where the unit status is genuinely unclear — a religion, a programming language, an economic-class signal, a literal alien biology proposal — and runs the same Price ratio they ran in Lesson 26. The deliverable is a defense of whether their candidate counts as a unit of selection, with the diagnostic as the evidence.
Words and genes both flow with migrants — the same math. In most places, words travel by migrants moving around. Alleles travel by migrants moving around. Both are heritable. Both accumulate random changes — in words by people changing pronunciation, in genes by mutation during reproduction. They're inherited together. So the geographic axis of greatest variation in words tends to match the geographic axis of greatest variation in genes. The math is the same. The mutation rate is different.
— 461_lec21_04
TODO: free-response panel. Provide template; student picks candidate; runs diagnostic; submits defense. Non-trivial code mod: build the cov(w, z) function for an arbitrary heritability-fitness-trait triple in R, then apply it to the student's chosen system.