Wednesday, August 13, 2008

Small World

There is a common — and inaccurate — belief that humans represent the apex of animal evolution. A typical representation of this anthropocentric bias is a diagram that shows a progression of animals: amphibian climbing from the water, dinosaur, bird, early mammal, ape, primitive man, and finally Homo sapiens.

Rather than thinking of ourselves as the tip-top point of the tree of life, it’s more accurate to imagine that we occupy a twig somewhere one of the many branches of a bush.

The real winners in the game of life-on-earth are, without a doubt, bacteria. True, it’s hard to fully appreciate organisms that are too small to see, but a few statistics make the point. Bacteria, or something very much like them, have lived on earth for some four billion years. They are found in rock as much as a mile below the surface (it’s possible that subterranean bacteria comprise the majority of the planet’s biomass); in clouds; in solid ice; in deep-sea hydrothermal vent water hotter than 220° F; in the radioactive water in nuclear reactor cores — almost everywhere. And they live in these places in unimaginable numbers. A gram of soil in our backyards may contain well over one billion bacteria. Our bodies, by cell count, are mostly bacteria. They outnumber our own (very) roughly 50 trillion cells by ten to one. Without bacteria, the biosphere would immediately – and perhaps totally — collapse. If humans were to vanish tomorrow, we’d hardly be missed.

What’s the point of all this? In part, it’s to point out that we tend to see the world in human-scale terms. Bacteria, fungi, protozoans and other microscopic organisms are much more important in our lives than large African predators, as fascinating as they may be. And don’t even get me started on parasites.

Is there a book here? Almost certainly. Will I write it? I have no idea. But if I don’t (or even if I do), someone else should. I look forward to reading it . . .


Unknown said...

“If humans were to vanish tomorrow, we’d hardly be missed.”

Well, things would certainly cool off pretty quick in a century or two. Without the deforestation, wetlands creation (from rice fields), landfill emissions, and fossil fuel burning, it would get downright chilly, according to a book I just read, Plows, Plagues, and Petroleum. It makes the case that without the human activity of the last several thousand years, we might be in an Ice Age right now. Very interesting stuff.

Anyway, great post, it’s good to be reminded about the huge impact of the tiny organisms. My current project has a cameo appearance by blue-green bacteria, but maybe I can work in some extremophiles...

steve jenkins said...

I'll check out that PPP book -- it sounds interesting. Based on historical ice age cycles, it does seem as if we're overdue for a major cool down.