[s28l]

The author is playing fast and loose with definitions here. Other sources[0][1] (that I would consider more reputable) define the breeder's equation in terms of populations, but this author focuses on arbitrary and ill-defined subsets of populations.

Crucially, the author defines R as "the response to selection", but he omits the second part: "from one generation to the next". Source [0] defines it even more clearly: "the change in the mean [of the population] over one complete generation".

Similarly, S is the difference in the measured trait among the entire population and the population that reproduces. So when the author considers "a set of parents with IQs of 120", it only fits the correct usage of the equation if we take that to mean that mean IQ of all parents in this generation is 120. If that's his argument, how is he defining the population of parents?

In my opinion, this is a wishy-washy argument that seems like a subtle way of advancing eugenics (or something similarly distasteful).

[0]: https://www.nature.com/scitable/knowledge/library/the-breede... [1]: https://public.wsu.edu/~gomulki/biol519/presentations/Sjober...

[civilized]

I'd like to understand what this comment is saying, but I can't follow. Could someone please explain more clearly what exact intellectual mistake the author allegedly made? The exposition in the OP seems very simple and clear, and I cannot seem to relate the definitional issues raised here to what is said in the article.

In the article's first thought experiment, we take a population with IQ 100, pull out the subset with IQ 120, have that IQ 120 subset breed with one another. According to the breeder's equation, we get children with average IQ 110. What is "arbitrary", "ill-defined", "fast and loose", etc. about this? It seems to be a standard application of the equation, no different than how one might breed cows for milk or tomatoes for size. It's quite unclear how the "crucial" clause "from one generation to the next" undermines any of this.

And could we perhaps focus on understanding what was said before muddying the waters with unsubstantiated accusations of eugenics? HN rules say that HN is for learning and understanding, not ideological warfare.

[s28l]

The breeder's equation described the expected change in a _population_ from one generation to the next due to selection pressures (natural or artificial).

For example, say a cattle rancher with a large herd may want to increase the average weight. So if he only breeds those animals in the top half of weight, what is the expected change in weight from one generation to the next?

For another example, say a particular species of lizard is hunted by a species of bird. The faster lizards are more likely to escape under a rock than the slower lizards. What is the expected change in average speed from one generation to the next?

Both of these examples have a well-defined _overall_ population and _reproducing_ population. The value of S can be calculated. In the first example, it is the difference between the mean weight of the top half of cattle and the mean weight of the entire herd. In the second example, it is difference in the mean speed of the lizards that are able to reproduce before being eaten and the entire population.

What are the analogous groups in the author's example? He doesn't define what distinguishes the population of 120 IQ parents from the population as a whole. In one reasonable reading, you could even think he means just two people when he says "a set of parents". That is what I mean about being fast and loose with terms: how are we defining the entire population and how are we defining the reproductive population?

Further, he says that 120 IQ parents having children with mean IQ of 110 is an example of regression to the mean. I would say the exact opposite: the 110 IQ children _define the mean_ of the next generation (in the correct usage of the equation). The expectation is that if there continues to be positive pressure on IQ, then future generations will continue to have increasing IQs.

With regards to "ideological warfare", the author himself explicitly introduced eugenics into the conversation with his analogy about the desert island populated by National Merit finalists (he literally described it as eugenics). His Wikipedia page [0] describes him as an anthropologist "who argues that cultural innovation resulted in new and constantly shifting selection pressures for genetic change, thereby accelerating human evolution and divergence between human races". I don't think it's unfair to say there are some unpleasant undertones to his work.

[0] https://en.wikipedia.org/wiki/Gregory_Cochran

[civilized]

> He doesn't define what distinguishes the population of 120 IQ parents from the population as a whole.

...Surely what distinguishes them is that they have IQs of 120, whereas the parent population has average IQ of 100?

> Further, he says that 120 IQ parents having children with mean IQ of 110 is an example of regression to the mean. I would say the exact opposite: the 110 IQ children _define the mean_ of the next generation (in the correct usage of the equation).

Surely you understand there is not only one mean in play here? There is also the mean of the population from which the IQ 120 subset was drawn. It is their mean that "regression to the mean" normally refers to, and has referred to since Galton invented the concept in 1886.

> With regards to "ideological warfare", the author himself explicitly introduced eugenics into the conversation with his analogy about the desert island populated by National Merit finalists

Not all things "eugenics" are inherently evil. Genetic screening of embryos to avoid infant suffering from horrible genetic diseases is also eugenics. Should mothers not have a choice to save their children from horrible genetic diseases?

It's ideological warfare to paint all eugenics with the same moral brush, as all having "unpleasant undertones". There is no moral flaw, per se, in seeking to understand how desirable traits might be increased in the human species.

I can't speak on whatever research the author has done on "human races", but it does not seem relevant to the discussion of the breeder's equation or to eugenics in the broad, perfectly benign sense of increasing desirable traits in a population.

[civilized]

PS: if anyone's interested in a meaningful, serious bioethical discussion of eugenics, I can highly recommend this paper: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8321981/