Origins of life on earth

The atmospheric conditions on the early Earth may have played an important role in the formation of components of nucleic acids, including the sugar ribose and the four nucleobases.

Origins of life on earth

Introduction cience shows us that the universe evolved by self-organization of matter towards more and more complex structures. Atoms, stars and galaxies self-assembled out of the fundamental particles produced by the Big Bang. In first-generation stars, heavier elements like carbon, nitrogen and oxygen were formed.

Aging first-generation stars then expelled them out into space — we, who consist of these elements, are thus literally born from stardust.

The heaviest elements were born in the explosions of supernovae. The forces of gravity subsequently allowed for the formation of newer stars and of planets.

Origins of life on earth

Finally, in the process of biological evolution from bacteria-like tiny cells the last universal common ancestor, abbr. LUCA to all life on earth, including us humans, complex life forms arose from simpler ones.


Upon considering this self-organization of material structures in the realm of philosophy, one may conclude that it happens either because the underlying laws of nature, which have to be exceedingly special to allow for it ReesSmolinSusskindsimply are the way they are possibly in the context of a multiverse or because they were designed by God for this purpose.

Since we know that the laws of nature are so self-sufficient that, based on them, the complexity of the entire physical universe evolved from fundamental particles, and further, complex life forms from simpler ones during biological evolution, we can reasonably extrapolate that they would also allow life itself to originate spontaneously, by chemical evolution of suitable structures — regardless if we believe these laws are designed or undesigned.

Therefore, we should expect an origin of life by natural causes from both theistic and atheistic philosophical perspectives. In the following decades, much impressive chemistry on the building blocks of life has been performed, but for a long time many crucial questions had been without experimental answers that might give hope for firm future directions.

Conceptually, the genesis of the protein translation system posed a fundamental problem. Yet in the last decade significant progress has been made in all those areas, even though details are still sketchy and problems persist on many issues.

Overall it can be said that puzzle pieces are starting to come together in such a way that the scientific assumption of a spontaneous origin of life from non-living matter finally has achieved plausibility on the level of experimental evidence.

While research in the field now appears vastly more promising than just a decade ago, the science on the origin of life is, compared to the science of biological evolution, still considerably underdeveloped in its explanatory power.

As Richard Robinson notes Robinson But beyond assuming the first cell must have somehow come into existence, how do biologists explain its emergence from the prebiotic world four billion years ago? Yet it is another thing entirely how, at the origin of life, they could have formed an initial organization by themselves step by step via whatever intermediary processes and building blocks.

One cannot lose out of sight that the most elementary cells we currently know, which are not permanently dependent on host-metabolism, the bacterium Mycoplasma genitalium, have protein-coding genes most bacteria, such as E. The likely most accurate hypothetical study Gil et al.

All the proteins produced from these genes are involved in a maze of pathways of metabolism, replication, as well as building and maintenance of structure, which is of bewildering complexity. In fact, how else than through such a minimum amount of complexity, could even a primitive cell have met the just mentioned basic demands?

Origins of life on earth

How could such a vastly complex network of more than proteins have arisen by itself? Yet evidence suggests that all this complexity may have evolved, step by step, from very simple beginnings.

Conditions for synthesis of organic molecules on the early Earth Essential to the spontaneous origin of life was the availability of organic molecules as building blocks. These conditions were assumed to simulate those on the primitive Earth.

Observations of Jupiter and Saturn had shown that they contained ammonia and methane, and large amounts of hydrogen were inferred to be present there as well it is now known that hydrogen is the main atmospheric component of these planets.

These reducing atmospheres of the giant planets were regarded as captured remnants of the solar nebula and the atmosphere of the early Earth was assumed by analogy to have been similar. It was suggested that only in a reducing atmosphere like this, synthesis of organic molecules — also sugars and organic bases, building blocks of nucleotides — would have been possible in large amounts Chyba and Sagan Later research had cast doubt on the existence of a reducing atmosphere, and suggested a neutral atmosphere instead — see also Chybathe accompanying article to Tian et al.

Another recent study supports an early reducing atmosphere as well. Chondrites are primitive material from the solar nebula and are generally believed to be the building blocks of the Earth and other rocky planets, asteroids and satellites.

During and after planet formation, gases escape from the chondritic material due to high temperature and pressure. Systematic, detailed calculations on what these gases must have been show that they are mainly the highly reducing hydrogen, methane and ammonia — the same gases as in the Miller-Urey-type experiments Schaefer and Fegleysee also press release.

The composition of the gases varied with temperature only to a moderate extent, and was found to be largely independent of the actual pressure under which outgassing may have occurred, which appears to support robustness of the conclusions. The authors mention that it had been found that a reducing atmosphere of methane and ammonia is extremely vulnerable to destruction by UV sunlight Kuhn and AtreyaKasting et al.

They also point out, however, that recent developments suggest that a reducing atmosphere is more stable than previously believed: Such a haze layer could also have been produced on the early Earth from outgassed methane and ammonia ZahnleSagan and ChybaPavlov et al.This story is part of BBC Earth's "Best of " list, our greatest hits of the the full list..

How did life begin? There can hardly be a bigger question. For much of human history. The long geological isolation of the Socotra archipelago and its hot and dry climate have combined to create a spectacular landscape with white sandy beaches that rise to limestone plateaus full of caves, and a rare, endemic flora.

RNA ON THE EARLY EARTH. According to the RNA World Hypothesis, RNA was a key molecule that was utilized by the earliest life on Earth to store genetic information and to catalyze chemical raises the question, however, of how RNA formed under prebiotic conditions on the early Earth.

In fact, the issue of the complete synthesis of RNA nucleotides has been a major stumbling . The term "evolution" usually refers to the biological evolution of living things. But the processes by which planets, stars, galaxies, and the universe form and change over time are also types of "evolution." In all of these cases there is change over time, although the processes involved are quite.

From fossil evidence, it appears that life may have existed on Earth as early as billion years ago. This suggests that life must have evolved sometime during Earth's tumultuous first billion years. Life on Earth began more than 3 billion years ago, evolving from the most basic of microbes into a dazzling array of complexity over time.

But how did the first organisms on the only known home to life in the universe develop from the primordial soup? One theory involved a "shocking" start.

Another idea is .

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