We work to serve the microbes

This is a repetitive book written for new parents of the upper middle class. It takes fascinating science with a transformative understanding of what it is to be human and answers redundant questions about babies, dogs, diapers, and birth. I read this book to better understand Sandra Blakeslee’s effect on popular understanding of science, because she is possibly the most respected popular science writer in America today. She is really good at making nice sentences that are easy to read and I bet she helped get this project off the ground, which is admirable in itself. Emotionally, this book is much better reading than the relevant wikipedia pages, even if the content is about as rich. I blame the publisher for the awful focus on babies, classist myopia, and the total omission of more interesting topics such as sex and Komodo dragons.

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Microbial mats can grow to be enormous colonies or can just live all over your dang body.
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Wikimedia diagram of which types of microbes live in what part of your skin. This diagram doesn’t even include things inside your body. The microbiota are very diverse and varies considerably between locations.


The microbes in one area, such as your gut, form an ecosystem, which the authors compare to a rainforest. Some microbes produce things others eat, some eat each other, some like one niche or prefer another. As this ecosystem is inside you, you are its environment and it can have an impact on you. Some gut microbiomes are correlated with obesity, autism, or other disorders. In particular, you can transfer microbes from one gut to another and make a lean mouse obese or obese mouse lean! Fecal matter transplants are not well understood for humans but are promising.

Dirt is Good

The titular claim comes down to a very weak anecdote, that eating a slurry of dirt from your homeland and water may help with traveler’s diarrhea. Generally, the microbes in dirt wouldn’t survive in your body, so they largely pass through but may have positive (safe for human) interactions with your microbiome first.


This is a bit weird, but swallowing microbes in yogurt can change the balance of your microbiome. It’s like importing animals to island countries, sometimes you get an invasive species and sometimes you get a good contributor and sometimes the new dudes just die. Seems to conflict with the “your microbiome is stable” claim, but the idea is that probiotics can restore stability during periods of weirdness.

Kids and Stuff

Sadly, dirt is mostly just good for kids. Children who suck their thumb (even as teenagers) have stronger immune systems and less allergies because they are eating small amounts of random microbes all the time. Children who grow up with dogs and farm animals get similar results, for similar reasons.
There is a tiny moment of speculation that a civilization with dogs will have an advantage over one without, because it’s been exposed to the dog microbes. But they don’t go far with this and it’s really tantamount to the usual cosmopolitan advantage with germs and imperial adventure.

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Most of the book is like this. I personally find this page to have no content worth remembering, so would call it “fluff.” Make your own call.

Conclusion: Read Other Sources

I’m left with a better understanding of the role of a (top notch) popular science writer: translate this new body of scientific research into a book one rich person can buy for another so they both feel that their decisions are based on objective thought and the greatest their civilization has to offer. I’m sure Blakeslee is capable of more, but I certainly respect how a book like this has a shot at readership and even mass sales if the right marketing events were to happen with it. Realistically, though, I probably would have learned more about microbes by reading wikipedia for an equal period of time. For instance, Wikipedia is much stronger on the Hygiene Hypothesis, microbiota of buildings, and generally more holistic consideration of health topics.


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