Science Literature

In June 2005, biophysicist David Deamer and colleagues visited a pool of water heated by volcanic activity on Russia's Kamchatka Peninsula. The scientists were under the impression that the water was sterile and that volcanism had erased all signs of life. "Darwin proposed that life started in 'a warm little pond'. . . . We are testing his theory in 'a hot little puddle'," Deamer related at a meeting of the Royal Society in London in February 2006. The group poured a "primordial soup" of proteins, DNA, and cell membranes into the pool and waited to see what would happen.

"When the scientists sampled the water after a few hours, they were surprised to find that most of the added material had disappeared. Tests revealed that the missing ingredients were bound to the clay that lined the tiny pond. The molecules "are nailed down, so they can't interact," Deamer says. As a result, hot volcanic pools may be unlikely spots for the first assembly of life's little bits, says Deamer." (source here)

David Deamer pours a "prebiotic soup" of chemicals into a volcanic pool in Kamchatka, Russia, to test a hypothesis about the origins of life. (Photo by Tony Hoffman, source here)

With this anecdote, Robert Shapiro commences his review of Deamer's latest book: First Life: Discovering the Connections between Stars, Cells, and How Life Began. Actually, Deamer refers also to the incident in the book and describes it as a "reality check". It taught him that natural systems are quite different from the laboratory and although numerous papers have been published on abiogenesis in the lab, the authors have failed to grapple with the principle that "we cannot translate lab results to natural settings".

"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."

The dominant contemporary theoretical approach to abiogenesis is known as the RNA World. The basic idea is that an RNA strand appeared spontaneously in the Archaean era of the early Earth. This RNA molecule had the ability to replicate itself. Shapiro says: "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." There are chemical problems just getting the RNA strand, but added to this are the problems of achieving replication. This is why some scientists have chosen to opt out of the RNA World paradigm and attempt to develop a rather different approach.

"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."

So, Deamer's book plows a new furrow. He considers the cell has to come first, so looks for ways of constructing a cell-like compartment. He does not like the deep-oceanic vent approach to doing this, because he considers hot seawater to be a liability, not an asset. Inside this cell-like structure, he seeks to form a self-replicating polymer.

"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."

That last comment from Shapiro reveals that he is not very impressed with Deamer's alternative proposal. But he also knows that a review is not the best platform to promote one's own approach. So the conclusion majors on a plea for more realism about the demerits of the RNA World and less deductive thinking about the nature of Archaean geochemistry.

"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."

This is good advice for all students of Earth history. There may be a consensus about the RNA World, but it is not a consensus based on evidence. The approach is supported by synthetic proofs drawn from unrealistic laboratory experiments, showing all the signs of a dogmatism that pastes its ideas on to nature. At our present state of understanding the issues, it is realistic only to acknowledge the tentativeness of all current theories of abiogenesis.

Astrobiology: Life's beginnings
Robert Shapiro
Nature, 476, 30-31, (04 August 2011) | doi:10.1038/476030a

Abstract: Robert Shapiro on a reminder that laboratory experiments don't always translate to nature.

Book reviewed: First Life: Discovering the Connections between Stars, Cells, and How Life Began, David Deamer, University of California Press: 2011. 288 pp. ISBN: 9780520258327

See also:

Luskin, C. Presto! The Origin of Life in Four Surprisingly Easy Steps, Evolution News & Views, August 8, 2011