Comment by robocat

8 days ago

Nothing about evolution feels sensible or right: and the vast majority of people have severe misunderstandings about how it works (for example the Darwin awards are highly misleading). Even science reporting is often highly misleading[0]. Intuition is not trustworthy for this topic, and neither is our ambient knowledge.

  and one group ate their dead relatives’ brains at funerals so consistently that they gave themselves a mad cow type disease called kuru, which killed a large percentage of their population and then, within a few generations, evolved a genetic mutation[1] that protects against it, one of the fastest cases of natural selection ever documented in humans

Referencing the Wikipedia article on kuru which references this paper: https://researchonline.lshtm.ac.uk/id/eprint/4514/1/nejmoa08...

The suggested evolution is:

* there is one ancestor with a gene that protects against kuru.

* children and mothers without that ancestor often die from kuru

* children of that ancestor have a much higher chance of survival

* eventually everyone is a child of that ancestor

* any children of that ancestor that didn't get the protective gene also eventually die out

The gene is selected for. There are no population effects.

The key part in the paper is where they mention adult men with the gene, because they are measuring the counterfactual of the many males that died because they didn't have that gene (males that ate brains as young kids but then died because they didn't have the gene from that ancestor).

The paper is hard to understand in part because of the confounding effects of males not eating the brains. Plus the confounder of stopping cannibalism in 1960.

The idea of "Group selection" is fundamentally wrong - regardless of how sensible the belief feels. Anybody using the words "group selection" is indicating their belief system, and they usually then have biased narratives to 'support' their belief.

[0] horrifically incorrect sciencedaily link in Wikipedia.

[1] We don't fucking evolve genetic mutations

7 comments

robocat

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HarHarVeryFunny  8 days ago

Fundamentally evolution is selecting for genes, not individuals, and there is no 1:1 relationship between genes and individuals.

Let's say that everyone has a skin color gene that makes them either red or blue. And a new predator turns up that only eats blue things. To you this is a tale about individuals, while it seems that an equally valid, and frankly preferable, view is this this isn't about individuals - it's about being red or blue and is a species level effect.

  • robocat  8 days ago

    I suspect the underlying issue is that we are all terrible at unthreading cause from effect.

    Words matter. Talking about "species level" is misleading because talking about an effect (blue phenotype) distracts us from the cause (a gene for blue).

    And evolution is confusingly another step removed: the red survives because the blue did not.

    Most of us struggle to see the counterfactual absence of a something.

    The blue "species" never exists - our brains want to find groups and patterns. Our words mislead us.

    The same thing is alluded to in the paper: the deaths of people without the gene is what is driving the gene to spread (through reproductive success of those that didn't die).

    Reproduction is what matters (which death or sickness may interfere with).

    Even the paper is confusing because it talks about 50 year old women (measuring survival bias; not whether they are expected to pass on genes at 50).

    (reedits for clarity).