First Life: Discovering the Connections between Stars, Cells, and How Life Began

  • David Deamer
University of California Press: 2011. 288 pp. $28.95, £19.95 9780520258327 | ISBN: 978-0-5202-5832-7

In June 2005, a group of international scientists clustered around a small, near-boiling pool in a volcanic region of Siberia. Biochemist David Deamer took a sample of the waters, then added to the pool a concoction of organic compounds that probably existed 4 billion years ago on the early Earth. One was a fatty acid, a component of soap, which his laboratory studies suggested had a significant role in the origin of life.

Over several days, Deamer took many more samples. He wished to see whether the chemical assembly process that he had observed in his laboratory, which eventually produced complex 'protocell' structures, could also take place in a natural setting. The answer was a resounding no. The clays and metal ions present in the Siberian pool blocked the chemical interactions.

This experiment was a reality check, explains Deamer in First Life. He proposes in the book that the complex molecules that led to life developed not in 'warm little ponds', but in tiny droplets bound by fatty acids. Although his account lacks the tales of personality and conflict that enliven other works in astrobiology, Deamer's demonstration that we cannot translate lab results to natural settings is valuable.

Biochemist David Deamer poured chemicals into a hot pool in 2005 to see if primitive cells would form. Credit: T. HOFFMAN

Because we can get reactions to work in the controlled conditions of a laboratory, he cautions, it does not follow that similar ones occurred on prebiotic Earth. We might overlook something that becomes apparent when we try to reproduce the reactions in a natural setting. This provocative insight explains why the origin-of-life field has been short on progress over the past half century, whereas molecular biology has flourished.

Today, the simplest living cells depend on molecules that are far more intricate than those that have been isolated from sources unrelated to life (abiotic), such as meteorites. The most noteworthy chemical substances in life are functioning polymers — large molecules made of smaller units called monomers, connected in a specific order. The nucleic acids RNA and DNA, carriers of genetic information and heredity, are made of connected nucleotide monomers. Similarly, proteins are vital polymer catalysts that are made by combining monomer amino acids. Such modern biological constructions were unlikely to have been present on the early Earth.

The advantage of the 'RNA world' idea is that one polymer would be all that was needed to get life started.

Despite this, many researchers have tried to demonstrate that RNA, or something similar, turned up spontaneously between 3 billion and 4 billion years ago. Physicist and biochemist Walter Gilbert suggested in 1986 that life began with the spontaneous generation of an RNA that could copy itself: the 'RNA world'. The advantage of this idea is that the formation of just one polymer would be all that was needed to get life started. The disadvantage is that such an event would be staggeringly improbable.

Nucleotides, for example, are not encountered in nature beyond organisms or laboratory synthesis. To construct RNA, high concentrations of four select nucleotides would be needed in the same location, with others being excluded. If this is the prerequisite for life, then it is an unusual phenomenon, rare in the Universe. As an alternative, other scientists (myself included) have suggested that life started without the presence of polymers; that instead, heredity and catalysis began with monomers.

Deamer's thesis diverges from the standard RNA-world concept. He focuses not on the generation of a naked RNA-like polymer, but on the formation of a simple cell-like compartment, or vesicle. Modern cells are enclosed by a complex fatty membrane, which prevents leakage. Vesicles with similar properties have been formed in the lab from certain fatty acids. Deamer holds that the spontaneous formation of vesicles, into which RNA could be incorporated, was a crucial step in life's origin. Unfortunately, his theory retains the improbable generation of self-replicating polymers such as RNA.

Nevertheless, Deamer's insight deflates the synthetic proofs put forward in numerous papers supporting the RNA world. He ends First Life by calling for the construction of a new set of biochemical simulators that match more closely the conditions on the early Earth. Unfortunately, the chemicals that he suggests for inclusion are drawn from modern biology, not from ancient geochemistry. We should let nature inform us, rather than pasting our ideas onto her.