The book is in four parts. Part 1, What is Living?, describes the 'redox' chemical process by which all life obtains energy. It depends on the oxidation of foodstuffs to generate ATP, the 'energy currency' of life. Textbook descriptions of this can easily seem dry and uninteresting, but Lane brings it to life by asking us to imagine being scaled down to a size where we can enter a heart muscle cell and see it as a huge factory, full of enormous complex machinery.
We find ourselves in a confined space like the engine room of a boat, packed with overheating protein machinery, stretching as far as the eye can see. The ground is bubbling with what look like little balls, which shoot out from the machines, appearing and disappearing in milliseconds. Protons! … You are at the thermodynamic centre of the cell, the site of cellular respiration, deep within the mitochondria.These protons are crucial to the production of ATP, and hence of the energy on which life depends. All living cells, of whatever kind, make use of it. But the extraordinary intricacy of these mechanisms and their interactions naturally prompts the question: how did all this evolve?
This is the subject of Part 2, The Origin of Life, where Lane describes his theory about life as having probably originated in White Smokers on the sea bed. These are less well known than the much-publicised Black Smokers, which are volcanic, acidic, and at high temperature. White Smokers are cooler, alkaline, and much longer-lived than Black Smokers and are not volcanic. Lane provides a detailed description of how life could have arisen in this way and explains that it would probably have done so early in Earth's history. It could also probably occur on the many other rocky planets in our galaxy. But that would not automatically entail the development of complex life forms.
Part 3, Complexity, tackles the puzzling question of why life remained at the level of protists (cells that lack a nucleus) for two billion years, before the appearance of eukaryotes (cells with a nucleus). The existence of large complex life forms, including us, could not occur until this happened. But why did it take so long?
The textbook story is that protists gradually became more and more complex until they were able to give rise to eukaryotes. But Lane is clear that this could not have happened; protists did become more complex but they had built-in limitations that meant they could not achieve the size or complexity of eukaryotes. His view is that the decisive event was the incorporation of bacteria into another type of cell, an archaeon. (There are two main domains of protists, bacteria and archaea, which look similar to each other but are evolutionarily distinct.) This was a one-off, very improbable, event. The hybrid cell eventually became a eukaryote, with a central nucleus, while the bacteria it contained developed into our mitochondria.
This happened quite suddenly in evolutionary terms, without a preliminary build-up. There are no intermediates between protists and eukaryotes, a situation that Lane describes as a biological black hole. In a vivid analogy he compares it to what we would think if all our inventions and institutions could be traced back to ancient Rome but there was nothing before but primitive hunter-gatherer societies.
Imagine that experts have spent decades scrutinising the archaeology of the world to unearth the remains of earlier civilisations that pre-dated the Romans, which would give some insight into how Rome was built. Hundreds of examples were discovered yet each one on closer inspection turned out to post-date Rome. All these outwardly ancient and primitive cities were actually founded in the 'dark ages' by progenitors who could trace their own ancestors back to ancient Rome. In effect, all roads lead to Rome, and Rome really was built in a day.This fantasy, Lane says, is actually a pretty good analogy to how the complex 'city' that is the eukaryotic cell relates, or doesn't relate, to what existed before it appeared.
Not only was the new development sudden, it was also a lucky fluke that might never have happened.
There is no innate or universal trajectory towards complex life. The universe is not pregnant with the idea of ourselves. Complex life might arise elsewhere, but it is unlikely to be common, for the same reason it did not arise repeatedly here.As readers of Lane's earlier books will know, he sees the mitochondria as the key to an understanding of sex and death.
This view of life's history, a 4-billion-year story, places the mitochondria at the centre of the evolution of the eukaryotic cell. In recent years medical research has come to a rather similar view: we now appreciate the mitochondria are instrumental in controlling cell death (apoptosis), cancer, degenerative disease, fertility and much more.
The implications of this are discussed in Part 4, Predictions , where Lane considers why different kinds of organisms age at different rates. Flying animals (birds and bats) do well; rats do badly. This has to do with aerobic capacity; humans are more talented in this regard, which explains why we live longer than our relatives (chimpanzees and gorillas, whose aerobic capacity is less). The still much-touted idea that ageing is due to free radicals is no longer believed by serious researchers, and increasing your intake of anti-oxidants won't help. Free radicals are involved in the ageing process but not in the simple way the alternative health movement would have you believe. So shall we be able to prolong human life? Probably yes, although not indefinitely, contrary to what some enthusiasts believe. We may be able to live in good health to about 120 but not beyond that.
This is an extraordinarily rich book, whose implications stretch well beyond the strictly biological. The style is informal but there is no shirking of complex ideas, so one has to take one's time in reading. The vivid analogies help here and the effort the book demands is repaid amply. It is not necessary to have read Lane's previous books in order to understand the arguments in this one, although I think some readers may wish to go back at least to Power, Sex, Suicide if they have not previously read this.