It's pretty hard to untie the multiple connections and ascribe specificity to brain development and lack of a decent gut microbiome.
For example, we know pretty well that humans subjected to famine/malnutrition/toxin exposure/etc. in the first two years of life, when ~70% of brain development takes place, will tend to have decreased cognitive function over their lifetime.
If being deprived of a microbiome reduces the ability of the gut to absorb nutrients, then essentially a kind of starvation could take place which reduces brain development, and as healthy brain development seems to be one of the requirements for normal social interactions with others, it could just be nutrient starvation rather than any direct neurochemical signaling from gut microbes to neurons that's messing up brain development.
There have been some experiments on megadosing probiotics to help with social anxiety disorder (SAD). There is at least this one guy who says it fixed it completely. He makes a megadose by growing specific probiotics in milk.[0]
This is different however, because the article talks about early brain development and autism spectrum disorder (ASD). Maybe early microbiome disruption -> ASD, later -> SAD?
Would really like to see him subject himself to an RCT of it, though - he could have someone else mix some strong flavor into the beverage to mask the taste difference from a placebo.
I recall there's a thing where those that undergo major gut surgery, which would disturb the gut biome, have a much higher chance of falling into substance use disorders afterwards.
Though a lot of gut surgery would be for bariatric weight loss, so there could be many other drivers for that correlation.
I’ve wondered whether a colonoscopy (prep for which which completely empties the gut through the use of heavy laxatives) could strongly affect your gut biome.
Gut microbiome is linked to autism. Eating probiotic l.reuterinmay may help. L.reuteri does this by upregulating host oxytocin levels which rewards social behavior.
I thought that relationship was no longer believed. It's just that autistic people may eat differently causing gut biome to be different. (Sorry I don't have time to source it.)
Wild speculation: perhaps particular foods and the gut microbiota they promote influence social structures. Perhaps one could ensure the spread of these feelings via ritual distribution of carefully prepared samples of some food... bread, say.
What happens when the magic starter culture is lost and the ritual no longer has the effect it used to?
Which is fascinating! And we know that gut micro biome has impacts on humans too.
But, we shouldn't extrapolate from research in fish all the way to humans until we can show it. The painful (or joyful) thing about science is dealing with the uncertainty and knowing that hypotheses are just that.
The fact this was in fish doesn't mean we can't use this as the start of a model in humans. While it isn't a 1:1 correlation, zebrafish make good model organisms in part due to their genetic similarities to humans.
There's obviously flaws with model organisms, as the saying goes "mice lie and monkeys exaggerate" but zebrafish are surprisingly good organisms to study human problems.
I don't think this is a problem with any of the "inmice" articles, and they are indeed very interesting to read! The only issue is that they forget to mention this small, but important detail in the title.
Which, despite the awesome rhyming phrase, doesn't really represent reality much. But even if it did, feral stage development wouldn't be reason to believe that this applies to humans.
The better reason to believe there's a chance this applies to humans, to some degree, is that humans and fish share similar brain signaling and micro biome products; which may be true or may not be! It's a big hint of a direction to look, which is great.
But even if this doesn't apply to humans, it's valuable research because it defines what's possible in biology.
Given that there are organisms that can literally effect human and animal behavior, in a way the system itself is partly controlled by the organisms inside it.
The big ones are toxoplasma, rabies, etc but there's a theory that many viruses and bacteria seek to control the behaviour of the host to enable successful spread. Perhaps flu makes people more social before they get too ill? Perhaps some sexually transmitted diseases change behaviour to make the host more promiscuous? Almost impossible to perform any studies on humans, but for fish...
Because there are different types of bacteria that are vying for domination. The "good" bacteria are fine with antibiotics because they usually only get used when there are too many "harmful" bacteria that threaten the life support system.
Penicillin did, but I think a lot of the newer ones were derived from bacteria. But doing a quick web search right now I'm mostly getting potential new antibiotics that came from bacteria, rather than proven antibiotics, so now I'm wondering about the actual bacterial contribution...
For example, we know pretty well that humans subjected to famine/malnutrition/toxin exposure/etc. in the first two years of life, when ~70% of brain development takes place, will tend to have decreased cognitive function over their lifetime.
If being deprived of a microbiome reduces the ability of the gut to absorb nutrients, then essentially a kind of starvation could take place which reduces brain development, and as healthy brain development seems to be one of the requirements for normal social interactions with others, it could just be nutrient starvation rather than any direct neurochemical signaling from gut microbes to neurons that's messing up brain development.