Review
31 Aug 2015

Microbes reconsidered

Bill Condie reviews Life's engines, a book about the importance of microbes to evolution.

Life’s engines: How microbes made Earth habitable,
by Paul G. Falkowski
Princeton University Press (2015)

Long before there were humans – or dinosaurs, or plants – there were the microbes. In fact, as Paul Falkowski reminds us, for almost four billion years, microbes had the Earth to themselves, busily transforming the chemistry that would pave the way for the arrival of all living things.

Falkowski brings a formidable breadth of scientific understanding to the task of explaining this, having worked as a biologist, an oceanographer and an astrobiologist. He moves easily between biological and earth sciences to help us understand the steps microscopic single-celled organisms took to make the planet habitable.

But clearly his first and greatest love is, as he describes it, “getting under the hood” to work out what makes the machinery inside living cells work. He says this is somewhat analogous to trying to understand what makes a car function if you start with no notion of the internal combustion engine, adding “cells are a lot more complicated than cars”.

And in that complexity lies the explanation of how we, and all living organisms, are here today.

Falkowski likens the driving force of a cell to a nanomachine and describes how cells and their nanomachine engines have been assembled from the simple to the complex in all animals and plants. In this way, he explains, we are all the sum total of the microbes that made us.

His book is also a fine lesson in the history of science, taking us through the discoveries that have given us insights, if not a complete understanding, of the basic building blocks of life.

As has become almost mandatory in any discussion of evolution, Life’s Engines comes with a warning. Falkowski believes microbes have the power to cope with change and that “the world of microbes will proceed to carry out their functions and come to new steady states, whereby their metabolism maintains a habitable planet”.

But he is concerned about our genetic tinkering with microbes when “we don’t understand what we are doing”. Falkowski argues that the problem lies with the approach of synthetic biologists, who do not concern themselves with Earth systems but with specific tasks within them – making a microbe that can better fix nitrogen, for example, or one that can carry out the task of photosynthesis more efficiently.

He acknowledges that for the most part these are “noble attempts to develop a future that is sustainable for humans” but he also fears that we are courting a potential disaster of unintended consequences. “Microbes have made this planet habitable for themselves and, ultimately, us. We are only passengers on the journey; however, we are tinkering with the organisms at the controls.”

Bill Condie is Spectrum editor of Cosmos and edits the Cosmos news blog.