Quotable (#215)

A life-gripped planet:

By controlling the chemical state of the atmosphere, life has also altered the rocks it comes into contact with, and so oxygenated the crust and mantle of Earth. This changes the material properties of the rocks, how they bend and break, squish, fold, and melt under various forces and conditions. All the clay minerals produced by Earth’s biosphere soften Earth’s crust—the crust of a lifeless planet is harder—helping to lubricate the plate tectonic engine. The wetness of Earth seems to explain why plate tectonics has persisted on Earth and not on its dry twin, Venus. One of the more extreme claims of the Gaia camp, at present neither proven nor refuted, is that the influence of life over the eons has helped Earth hold on to her life‐giving water, while Venus and Mars, lifeless through most of their existence, lost theirs. If so, then life may indeed be responsible for Earth’s plate tectonics. One of the original architects of plate tectonic theory, Norm Sleep from Stanford, has become thoroughly convinced that life is deeply implicated in the overall physical dynamics of Earth, including the “nonliving” interior domain. In describing the cumulative, long-term influence of life on geology, continent building, and plate tectonics, he wrote, “The net effect is Gaian. That is, life has modified Earth to its advantage.” The more we study Earth, the more we see this. Life has got Earth in its clutches. Earth is a biologically modulated planet through and through. In a nontrivial way, it is a living planet.

Quotable (#186)

Ed Yong’s microbe book, I Contain Multitudes, is stunningly good. Among hundreds of quotable passages, this (p.84) seems of exceptionally general relevance:

We like our black-and-white narratives, with clear heroes and villains. In the last few years, I’ve seen the viewpoint that “all bacteria must be killed” slowly give ground to “bacteria are our friends and want to help us”, even though the latter is just as wrong as the former. We cannot simply assume that a particular microbe is “good” just because it lives inside us. Even scientists forget this. The very term symbiosis has been twisted so that its original neutral meaning — “living together” — has been infused with positive spin, and almost flaky connotations of cooperation and harmony. But evolution doesn’t work that way. It doesn’t necessarily favor cooperation, even if that’s in everyone’s interests. And it saddles even the most harmonious relationships with conflict.