"Any simple major enhancement to human intelligence is a net evolutionary disadvantage."
An individual who is more intelligent might be less likely to pass on their own genes, but may well make the species as a whole more resilient. Looking at evolution from the perspective of the individual is a mistake.
Would you care to support your assertion that "looking at evolution from the perspective of the individual is a mistake"? The individual is the fundamental "biological unit" through which human genes are propogated (same for non-genetic vectors of heritable traits, such as epigenetic signatures and memes), and the individual is also the level at which selection acts. Since evolution is all about selection of and propogation of genes, in what sense is it a mistake to look at evolution at the level where both of these phenomena act?
Note that being "less likely to pass on their own genes" means exactly the same thing here as having a "net evolutionary disadvantage", so your comment is actually agreeing with the sentence that you quoted, despite what appears to be your intent.
Regardless, there is a valid discussion to be had about evolution at levels other than the individual, but it's just not as simple as replacing individuals with species as the biological unit of evolution.
An individual does not evolve, it either reproduces or not. Individuals have never been the "biological unit" of evolution; evolution is a process of populations by definition.
Edit: To make it a little more clear what this means, treating the organism as the unit of evolution is like treating the cell as the unit of walking. Yes, walking is the action of individual cells, but nothing interesting or relevant to the process is happening at a cellular level.
Correct, an individual does not evolve, but the process of evolution is the result of selection on and reproduction of individuals. You can't just change it to be about selection on and reproduction of populations and then treat the individual-level stuff as an implementation detail that you can ignore.
Evolution is the result of the reproduction of populations of individuals. A single organism reproducing once is a non-event, evolutionarily speaking.
This implies effects in the population that are counterintuitive from the perspective of the individual, which is why it's important to make the distinction.
>> A single organism reproducing once is a non-event, evolutionarily speaking.
True, but a single organism with a new trait failing to reproduce means that the trait cannot be passed on, and therefore does not exist in the population in an evolutionary sense. You absolutely can't ignore individuals in the evolutionary process.
Well, it's much more controversial than that-- but perhaps I'm to blame, because it's also more controversial than I've been trying to claim.
Perhaps the more neutral framing is this: There are things that happen to life which you will not be able to explain using a primarily gene-, individual-, or group-centered perspective. This is because evolution is complex, and anyone who claims to really understand it is lying.
I've been advocating for the population perspective mainly because it necessarily includes what's going on at a lower level, but the safer truth is simply that anything you think you know on the basis of theory needs to pass through many levels of analysis, and then be filtered with a healthy dose of what really happens.
How would helping "the species as a whole" increase the frequency of that person's genetic traits in the population? It sounds very pretty and virtuous -- get ahead by helping others, hooray -- but the math just doesn't work.
This could work through group selection - on average, groups containing more intelligent individuals would outcompete groups not containing them. However, this requires a scenario with group competition, and probably also requires substantially more time than individual selection for the dynamic to play out.
How so? Having the sickle cell trait (i.e. being heterozygous for the gene which, in homozygous individuals, causes sickle cell anemia) gives an advantage to individual evolutionary fitness in areas where malaria is a big problem. There's no need for group selection arguments to explain the prevalence of that trait.
An individual who is more intelligent might be less likely to pass on their own genes, but may well make the species as a whole more resilient. Looking at evolution from the perspective of the individual is a mistake.