Elements for the Origin of Life on Land: A Deep-Time Perspective from the Pilbara Craton of Western Australia

N. C. Wickramasinghe ( Department of Applied Mathematics and Astronomy, University College, Cardiff, U. K. ). The question of the origin of life is, of course, one of the most important scientific questions and it is also one of the most difficult. One is inevitably faced here with a situation where there are very few empirical facts of direct relevance and perhaps no facts relating to the actual transition from organic material to material that can even remotely be described as living. The time perspective of events that relate to this problem has already been presented by Dr Chang. Uncertainty still persists as to the actual first moment of the origin or the emergence of life on the Earth. At some time between 3800 and 3300 Ma BP the first microscopic living systems seem to have emerged. There is a definite moment in time corresponding to a sudden appearance of cellular-type living systems. Now, traditionally the evolution of carbonaceous compounds which led to the emergence of life on Earth could be divided into three principal steps and I shall just remind you what those steps are. The first step is the production of chemical building blocks that lead to the origin of the organic molecules necessary as a prerequisite for the evolution of life. Step two can be described in general terms as prebiotic evolution, the arrangement of these chemical units into some kind of sequence of precursor systems that come almost up to life but not quite; and then stage three is the early biological evolution which actually effects the transition from proto-cellular organic-type forms into truly cellular living systems. The transition is from organic chemistry, prebiotic chemistry to biochemistry. Those are the three principal stages that have been defined by traditional workers in the field, the people who, as Dr Chang said, have had the courage to make these queries and attempt to answer them. Ever since the classic experiments where organic materials were synthesized in the laboratory a few decades back, it was thought that the first step, the production of organic chemical units, is important for the origin of life on the Earth, and that this had to take place in some location on the Earth itself.

Download Full-text

Deep Time Paleobiology: Stromatolites–A Key to Decoding Primitive Ecosystems on Earth and Beyond

The Paleontological Society Papers ◽

10.1017/s1089332600001601 ◽

2008 ◽

Vol 14 ◽

pp. 55-65 ◽

Cited By ~ 1

Author(s):

Abigail C. Allwood

Keyword(s):

Fossil Record ◽

New Techniques ◽

Deep Time ◽

Microbial Ecosystems ◽

Planktonic Form ◽

The Origin Of Life ◽

The Rich ◽

Geologic Record ◽

Pilbara Craton ◽

Shed Light

Finding the beginning of Earth's fossil record is a long-standing palaeontological challenge arising from the quest to understand the origin of life. Research in recent years has necessarily focused on determining the existence (or otherwise) of fossils in the Early Archaean rock record. Nonetheless, despite numerous reports of microfossils(?) and stromatolites, consensus on the existence of life in the Early Archaean has been elusive (e.g. Moorbath, 2005). However, new techniques and approaches are allowing more confident interpretation of the Archaean fossil record, and the nature of the earliest biosignatures can be used to inform our understanding of emergent ecosystems on Earth and perhaps on other terrestrial planets.Evidence is mounting that microbial ecosystems may have had a firm foothold as early as ~3.5 Ga (Tice and Lowe, 2004; Schopf, 2006; Hofmann et al., 1999; Allwood et al., 2006, 2007b; Westall et al., 2006; Westall and Southam, 2006). Significantly, there is now also evidence that the Early Archaean record may not be as meager and cryptic as previously thought. For example, the 3.43 Ga Strelley Pool Chert of the Pilbara Craton of Western Australia contains kilometer-scale tracts of a fossilized stromatolite (microbial?) reef (Allwood et al., 2006, 2007b) and provides a large suite of evidence that is consistent with life's existence. Moreover, the rapidity with which the Strelley Pool reef established itself on a newly-submerged landmass suggests that life was well established by that time, waiting in the wings in planktonic form until conditions favored sessile biofilm formation. The rich vault of information in such rocks as the Strelley Pool Chert may shed light not only upon life's antiquity, but also on the nature of early organisms and ecosystems, the environments that nurtured them, the processes that aided preservation of biosignatures and the palaeontological approaches needed to interpret them. This in turn will be a valuable guide in the search for—and interpretation of—ancient microbial biosignatures in the geologic record of other planets or moons.

Download Full-text

The Tempo and mode(S) of Prebiotic Evolution

International Astronomical Union Colloquium ◽

10.1017/s0252921100014937 ◽

1997 ◽

Vol 161 ◽

pp. 419-429 ◽

Cited By ~ 1

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.

Download Full-text

Photochemical Evolution of Interstellar/Precometary Organic Material

International Astronomical Union Colloquium ◽

10.1017/s0252921100014585 ◽

1997 ◽

Vol 161 ◽

pp. 23-47 ◽

Cited By ~ 11

Author(s):

Louis J. Allamandola ◽

Max P. Bernstein ◽

Scott A. Sandford

Keyword(s):

Origin Of Life ◽

Building Blocks ◽

Complex Species ◽

Infrared Observations ◽

Interstellar Ice ◽

Polycyclic Aromatic ◽

Ultraviolet Photolysis ◽

The Origin Of Life ◽

Simple Molecules ◽

Complex Organic

AbstractInfrared observations, combined with realistic laboratory simulations, have revolutionized our understanding of interstellar ice and dust, the building blocks of comets. Since comets are thought to be a major source of the volatiles on the primative earth, their organic inventory is of central importance to questions concerning the origin of life. Ices in molecular clouds contain the very simple molecules H2O, CH3OH, CO, CO2, CH4, H2, and probably some NH3and H2CO, as well as more complex species including nitriles, ketones, and esters. The evidence for these, as well as carbonrich materials such as polycyclic aromatic hydrocarbons (PAHs), microdiamonds, and amorphous carbon is briefly reviewed. This is followed by a detailed summary of interstellar/precometary ice photochemical evolution based on laboratory studies of realistic polar ice analogs. Ultraviolet photolysis of these ices produces H2, H2CO, CO2, CO, CH4, HCO, and the moderately complex organic molecules: CH3CH2OH (ethanol), HC(= O)NH2(formamide), CH3C(= O)NH2(acetamide), R-CN (nitriles), and hexamethylenetetramine (HMT, C6H12N4), as well as more complex species including polyoxymethylene and related species (POMs), amides, and ketones. The ready formation of these organic species from simple starting mixtures, the ice chemistry that ensues when these ices are mildly warmed, plus the observation that the more complex refractory photoproducts show lipid-like behavior and readily self organize into droplets upon exposure to liquid water suggest that comets may have played an important role in the origin of life.

Download Full-text