Reflections on the Human Lake

Belated response to, and placefinder for, Carl Zimmer’s great article The Human Lake.

As the first commenter wrote: “excellent on so many axes”. Does what all science writing should do, regardless of the audience or context— communicates difficult concepts fluently, in this case making convincing connections between very different branches of biology.

And it managed something extra for me, when it took an entirely unexpected turn half way through. The piece first looks at some early history from the science of ecology, when a limnologist working in the 1930s named G Evelyn Hutchinson used a small glacial lake in Connecticut to further develop the pre-existing concept of the ‘ecological niche’.

So far so good.

Having the spent the last couple of years or so developing an interest in the wider determinants of health— the social, economic, and environmental— and noting the word ‘human’ in the title, I was primed for Zimmer’s article to take a similar direction, comparing the complex web of species interactions in the lake to the complex interconnections of the human environment, at an appropriately larger scale.

But no. Rather than going macro, Zimmer went micro: his ‘human lake’ is not a human economy or society, nor a human-influenced larger natural ecosystem, but a single human gut. Thousands of different species of bacteria can live in human intestines, where they perform a surprising number of different functions. The diverse potential interactions in this ‘microbiome’ can impact the host positively or negatively, and each person has a uniquely composed collection of intestinal fauna. They have different internal interactions, and respond to disturbances differently— much like the diverse ecosystems of Connecticut’s post-glacial lakes.

Fascinating stuff. On reflection, the other article— the one I was expecting from the title and the first few paragraphs— would be much harder to write, probably less focused, and probably less satisfying. Nonetheless, I’d love to see Zimmer (or someone else) give it a go one day. When analogous processes can be demonstrated to work at multiple scales and in multiple contexts, the evidence for their existence becomes more convincing; see consilience.


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