[_ywdj]

This feels like a just-so story.

There are perfectly plausible reasons why the conditions we regard as mental illness are adaptations that help evolutionary fitness:

- Depression puts one into a low-energy, contemplative state that enables reflection, healing and formulation of reformed ways of thinking and being ("dark night of the soul");

- Bipiolar is a pattern of swinging between high-energy bursts of inspiration and creation, and low-energy states of recuperation and reflection;

- Schizophrenia is a way of disassociating from real-world experiences that are too painful to experience with normal consciousness, and is a preferable alternative (from an evolutionary perspective) to suicide, buying time for processing and healing to take place, given the right kind of support.

Of course, that could be seen as a "just so" story too. Except that evolutionary theory says that only genes that promote evolutionary fitness should survive and spread through the genome, particularly given that replication of any given gene carries a significant cost. We can also easily observe that conditions like depression and schizophrenia normally develop in response to a trigger - i.e., a traumatic life event or extended period of abuse.

So, it's far less of a confected story to just accept that these conditions have been retained in the genome for the reason that makes most sense according to evolutionary theory: it's evolutionarily beneficial for them to be there.

[lkrubner]

"according to evolutionary theory"

Promoter genes are also part of evolutionary theory. You seem to think evolutionary theory came to an end in 1882. But a lot has happened since then.

[_ywdj]

First, I don’t know why you feel the need to include a hostile ad hom barb like “You seem to think evolutionary theory came to an end in 1882”.

I’ve done multiple Google searches and even done Google Books searches in the very book you linked, for the exact phrase “promoter gene”, and it really doesn’t seem to be a term that’s used, at all, really.

DNA promoters are well recognized, but not in the context you’re talking about.

I can very much understand the notion that genes may act to further their own propagation at the cost of the host’s fitness - sure.

It’s just that we first need to see evidence that it’s happening, by having a clear definition of what favours vs costs the host’s fitness.

The hypothesis you’ve cited (and from the book reviews it seems even the authors concede their hypotheses are highly speculative), seems to start with the assumption that these mental illness traits are opposed to the host’s fitness and confer no benefits whatsoever.

But all we have to do is point out the many cases in which these traits actually do benefit the host, which I did and you even conceded in the last line of your comment, and the hypothesis is void.

It reminds me of the “junk DNA” hypothesis, where researchers couldn’t find an obvious use for large sections of the genome so just assumed it to be useless and called it “junk”, only to be later found to have very important roles:

https://medicine.yale.edu/news/yale-medicine-magazine/articl...

https://www.quantamagazine.org/the-complex-truth-about-junk-...