The Origin of Life - Abiogenesis - Dr. Jack Szostak

No Viable Mechanism to Generate a Primordial Soup.

According to conventional thinking among origin-of-life theorists, life arose via unguided chemical reactions on the early Earth some 3 to 4 billion years ago. Most theorists believe that there were many steps involved in the origin of life, but the very first step would have involved the production of a primordial soup -- a water-based sea of simple organic molecules -- out of which life arose. While the existence of this "soup" has been accepted as unquestioned fact for decades, this first step in most origin-of-life theories faces numerous scientific difficulties.

In 1953, a graduate student at the University of Chicago named Stanley Miller, along with his faculty advisor Harold Urey, performed experiments hoping to produce the building blocks of life under natural conditions on the early Earth.1 These "Miller-Urey experiments" intended to simulate lightning striking the gasses in the early Earth's atmosphere. After running the experiments and letting the chemical products sit for a period of time, Miller discovered that amino acids -- the building blocks of proteins -- had been produced.

For decades, these experiments have been hailed as a demonstration that the "building blocks" of life could have arisen under natural, realistic Earthlike conditions,2 corroborating the primordial soup hypothesis. However, it has also been known for decades that the Earth's early atmosphere was fundamentally different from the gasses used by Miller and Urey.

The atmosphere used in the Miller-Urey experiments was primarily composed of reducing gasses like methane, ammonia, and high levels of hydrogen. Geochemists now believe that the atmosphere of the early Earth did not contain appreciable amounts of these components. UC Santa Cruz origin-of-life theorist David Deamer explains in the journal Microbiology & Molecular Biology Reviews:

This optimistic picture began to change in the late 1970s, when it became increasingly clear that the early atmosphere was probably volcanic in origin and composition, composed largely of carbon dioxide and nitrogen rather than the mixture of reducing gases assumed by the Miller-Urey model. Carbon dioxide does not support the rich array of synthetic pathways leading to possible monomers...3

Likewise, an article in the journal Science stated: "Miller and Urey relied on a 'reducing' atmosphere, a condition in which molecules are fat with hydrogen atoms. As Miller showed later, he could not make organics in an 'oxidizing' atmosphere."4 The article put it bluntly: "the early atmosphere looked nothing like the Miller-Urey situation."5 Consistent with this, geological studies have not uncovered evidence that a primordial soup once existed.6

There are good reasons why the Earth's early atmosphere did not contain high concentrations of methane, ammonia, or other reducing gasses. The Earth's early atmosphere is thought to have been produced by outgassing from volcanoes, and the composition of those volcanic gasses is related to the chemical properties of the Earth's inner mantle. Geochemical studies have found that the chemical properties of the Earth's mantle would have been the same in the past as they are today.7 But today, volcanic gasses do not contain methane or ammonia, and are not reducing.

A paper in Earth and Planetary Science Letters found that the chemical properties of the Earth's interior have been essentially constant over Earth's history, leading to the conclusion that "Life may have found its origins in other environments or by other mechanisms."8 So strong is the evidence against pre-biotic synthesis of life's building blocks that in 1990 the Space Studies Board of the National Research Council recommended that origin-of-life investigators undertake a "reexamination of biological monomer synthesis under primitive Earthlike environments, as revealed in current models of the early Earth."9

Because of these difficulties, some leading theorists have abandoned the Miller-Urey experiment and the "primordial soup" theory. In 2010, University College London biochemist Nick Lane stated that the primordial soup theory "doesn't hold water" and is "past its expiration date."10 Instead, he proposes that life arose in undersea hydrothermal vents. But both the hydrothermal vent and primordial soup hypotheses face another major problem.

To grasp the reality of life as it has been revealed by molecular biology, we must magnify a cell a thousand million times until it is twenty kilometers in diameter and resembles a giant airship large enough to cover a great city like London or New York. What we would then see would be an object of unparalleled complexity and adaptive design. On the surface of the cell we would see millions of openings, like the port holes of a vast space ship, opening and closing to allow a continual stream of materials to flow in and out. If we were to enter one of these openings we would find ourselves in a world of supreme technology and bewildering complexity.

The origin of primitive membranes is one of the more neglected fields in origin of life research. Although fatty acids can be produced under early earth conditions, they are quite resistant to assembly under conditions under which they are generated. In addition, these membranes fail to provide a reasonable mechanism for nutrient/waste transport or any way to produce a proton gradient, so that any "proto-cell" generated would soon die from an inability to use energy.