Searching for a shadow biosphere on Earth as a test of the ‘cosmic imperative’

2011 ◽  
Vol 369 (1936) ◽  
pp. 624-632 ◽  
Author(s):  
P. C. W. Davies
Keyword(s):  
Origin Of Life ◽  
Observable Universe ◽  
The Galaxy ◽  
Terrestrial Life ◽  
The Origin Of Life ◽  
Absence Of Evidence ◽  
Life On Earth ◽  
Second Genesis

Estimates for the number of communicating civilizations in the galaxy, based on the so-called Drake equation, are meaningless without a plausible estimate for the probability that life will emerge on an Earth-like planet. In the absence of a theory of the origin of life, that number can be anywhere from 0 to 1. Distinguished scientists have been known to argue that life on Earth is a freak accident, unique in the observable universe and, conversely, that life is almost bound to arise in the course of time, given Earth-like conditions. De Duve, adopting the latter position, coined the phrase that ‘life is a cosmic imperative’. De Duve’s position would be immediately verified if we were to discover a second sample of life that we could be sure arose from scratch independently of known life. Given the current absence of evidence for life beyond Earth, the best way to test the hypothesis of the cosmic imperative is to see whether terrestrial life began more than once. If it did, it is possible that descendants of a second genesis might be extant, forming a sort of ‘shadow biosphere’ existing alongside, or perhaps interpenetrating, the known biosphere. I outline a strategy to detect the existence of such a shadow biosphere.

scholarly journals Martian life: stuck somewhere between inevitable biochemistry and quirky biology

2004 ◽  
Vol 25 (1) ◽  
pp. 20
Author(s):  
Charles H Lineweaver
Keyword(s):  
Origin Of Life ◽  
Paradigm Shift ◽  
Black And White ◽  
The Origin Of Life ◽  
Life On Earth ◽  
Second Genesis

If traces of life are found on Mars, the question that needs to be asked is: How independent is this life from life on Earth? A paradigm shift is needed from ?Was there a second genesis?? to ?How much of one was there?? This abandonment of a picture in black and white to a more nuanced grey is based on the idea that the boundary between life and non-life was not sharp and that the origin of life was an extended process of molecular tinkering.

Life as a cosmic imperative?

2011 ◽  
Vol 369 (1936) ◽  
pp. 620-623 ◽  
Author(s):  
Christian de Duve
Keyword(s):  
Origin Of Life ◽  
Extrasolar Planet ◽  
Second Stage ◽  
Physical Chemical ◽  
Terrestrial Life ◽  
Probable Site ◽  
The Origin Of Life ◽  
Chemical Conditions ◽  
Life On Earth ◽  
Two Stages

The origin of life on Earth may be divided into two stages separated by the first appearance of replicable molecules, most probably of RNA. The first stage depended exclusively on chemistry. The second stage likewise involved chemistry, but with the additional participation of selection, a necessary concomitant of inevitable replication accidents. Consideration of these two processes suggests that the origin of life may have been close to obligatory under the physical–chemical conditions that prevailed at the site of its birth. Thus, an extrasolar planet in which those conditions were replicated appears as a probable site for the appearance of extra-terrestrial life.

The Tempo and mode(S) of Prebiotic Evolution

1997 ◽  
Vol 161 ◽  
pp. 419-429 ◽  
Author(s):  
Antonio Lazcano
Keyword(s):  
Origin Of Life ◽  
Organic Compounds ◽  
Biological Evolution ◽  
Current Evidence ◽  
Early Diversification ◽  
Time Period ◽  
The Galaxy ◽  
History Of ◽  
Widespread Phenomenon ◽  
The Origin Of Life

AbstractDifferent current ideas on the origin of life are critically examined. Comparison of the now fashionable FeS/H2S pyrite-based autotrophic theory of the origin of life with the heterotrophic viewpoint suggest that the later is still the most fertile explanation for the emergence of life. However, the theory of chemical evolution and heterotrophic origins of life requires major updating, which should include the abandonment of the idea that the appearance of life was a slow process involving billions of years. Stability of organic compounds and the genetics of bacteria suggest that the origin and early diversification of life took place in a time period of the order of 10 million years. Current evidence suggest that the abiotic synthesis of organic compounds may be a widespread phenomenon in the Galaxy and may have a deterministic nature. However, the history of the biosphere does not exhibits any obvious trend towards greater complexity or «higher» forms of life. Therefore, the role of contingency in biological evolution should not be understimated in the discussions of the possibilities of life in the Universe.

scholarly journals ‘Whole Organism’, Systems Biology, and Top-Down Criteria for Evaluating Scenarios for the Origin of Life

Life ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 690
Author(s):  
Clifford F. Brunk ◽  
Charles R. Marshall
Keyword(s):  
Origin Of Life ◽  
Top Down ◽  
Chemical Systems ◽  
Biochemical Pathways ◽  
The Origin Of Life ◽  
Energy And Material Flows ◽  
Complex Scenario ◽  
Life On Earth ◽  
Physical Laws ◽  
Equilibrium Chemical

While most advances in the study of the origin of life on Earth (OoLoE) are piecemeal, tested against the laws of chemistry and physics, ultimately the goal is to develop an overall scenario for life’s origin(s). However, the dimensionality of non-equilibrium chemical systems, from the range of possible boundary conditions and chemical interactions, renders the application of chemical and physical laws difficult. Here we outline a set of simple criteria for evaluating OoLoE scenarios. These include the need for containment, steady energy and material flows, and structured spatial heterogeneity from the outset. The Principle of Continuity, the fact that all life today was derived from first life, suggests favoring scenarios with fewer non-analog (not seen in life today) to analog (seen in life today) transitions in the inferred first biochemical pathways. Top-down data also indicate that a complex metabolism predated ribozymes and enzymes, and that full cellular autonomy and motility occurred post-LUCA. Using these criteria, we find the alkaline hydrothermal vent microchamber complex scenario with a late evolving exploitation of the natural occurring pH (or Na+ gradient) by ATP synthase the most compelling. However, there are as yet so many unknowns, we also advocate for the continued development of as many plausible scenarios as possible.

What is life?

1997 ◽  
Author(s):  
John Maynard Smith ◽  
Eors Szathmary
Keyword(s):  
Natural Selection ◽  
Origin Of Life ◽  
Definition Of Life ◽  
The Sun ◽  
Physical Processes ◽  
Living Things ◽  
Survival And Reproduction ◽  
The Origin Of Life ◽  
Definition Of ◽  
Life On Earth

Imagine that, when the first spacemen step out of their craft onto the surface of one of the moons of Jupiter, they are confronted by an object the size of a horse, rolling towards them on wheels, and bearing on its back a concave disc pointing towards the Sun. They will at once conclude that the object is alive, or has been made by something alive. If all they find is a purple smear on the surface of the rocks, they will have to work harder to decide. This is the phenotypic approach to the definition of life: a thing is alive if it has parts, or ‘organs’, which perform functions. William Paley explained the machine-like nature of life by the existence of a creator: today, we would invoke natural selection. There are, however, dangers in assuming that any entity with the properties of a self-regulating machine is alive, or an artefact. In section 2.2, we tell the story of a self-regulating atomic reactor, the Oklo reactor, which is neither. This story can be taken in one of three ways. First, it shows the dangers of the phenotypic definition of life: not all complex entities are alive. Second, it illustrates how the accidents of history can give rise spontaneously to surprisingly complex machine-like entities. The relevance of this to the origin of life is obvious. In essence, the problem is the following. How could chemical and physical processes give rise, without natural selection, to entities capable of hereditary replication, which would therefore, from then on, evolve by natural selection? The Oklo reactor is an example of what can happen. Finally, section 2.2 can simply be skipped: the events were interesting, but do not resemble in detail those that led to the origin of life on Earth. There is an alternative to the phenotypic definition of life. It is to define as alive any entities that have the properties of multiplication, variation and heredity. The logic behind this definition, first proposed by Muller (1966), is that a population of entities with these properties will evolve by natural selection, and hence can be expected to acquire the complex adaptations for survival and reproduction that are characteristic of living things.

The Origin of Life on Earth and in the Universe

2006 ◽  
pp. 147-198
Author(s):  
Jordi Llorca ◽  
Malcolm E. Schrader ◽  
Pasquale Stano ◽  
Francesca Ferri ◽  
Pier Luigi Luisi
Keyword(s):  
Origin Of Life ◽  
The Origin Of Life ◽  
Life On Earth ◽  
The Universe
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