The water was murky at first. Review of the book “How life on Earth was created”.

Jak powstało życie na Ziemi

In the second half of the 20th century. Polish popular science book market was not very rich. One of the more important items is In the beginning there was hydrogen by Ditfurth. This book describes the history of the Universe, including the origin of life. Nowadays, more items of this type are published, so it is harder for them to break out. Chances are How Life arose on Earth by two Januarys Weiner. The coincidence of the names is no coincidence – they are father and son.

How did life originate on Earth? – multiplicity of definitions an obstacle to specifics

The authors are not rookies and know how to write, so their book is a pleasure to read. I will immediately reveal “who killed”, or rather “who did not kill”, because the content does not answer the title question. It is impossible to say straightforwardly how life originated on Earth, because first one would have to establish a definition of life itself, and here there is no consensus. The authors invoke more than one definition, showing that life can be tried to be defined in many ways, focusing on slightly different details each time.

The classic problem is the issue of viruses that fulfill selected aspects from the definition of life, but not the most popular one – the requirement of their own metabolism. Viruses don’t have it; they rely on cellular organisms. But the authors don’t care – they insist that life is a collective process. No organism lives without a connection to the rest of the biosphere. The dependence of viruses on their hosts is extreme, but not enough for the authors to leave them out of the living world. More important to them seem to be those elements of the definition of life that emphasize its evolutionary nature.

Aquatic theories on how life arose on Earth

There is no answer to the question of how life originated on Earth, but the authors write how it might have gone. And this is where the water issues come in. Life as we know it is inextricably linked to water. Other versions are not bothered by the authors, leaving it in the realm of science fiction. They are not likely to be supporters of the thesis that life originated somewhere in interstellar dust and found its way to a cooling Earth. They do not rule out this possibility, but point out the weaknesses of this hypothesis. Assuming that life originated on Earth, water is its key environment and also a component.

Everyone is familiar with the more or less popularized hypothesis of primordial soup. It was formulated by Haldane and Oparin, and tested in the laboratory by Urey and Miller. These attempts failed to create life, only the various organic substances needed for metabolism. Today it is known that the assumptions about the composition of the atmosphere and ocean of the former Earth made in this hypothesis were wrong. It has historical value, but few try to defend it by modifying it with newer findings.

It is different with later hypotheses. The one about black hydrothermal vents probably has the most supporters. Unlike the primordial soup, where life would be thought to arise at the interface between the hydrosphere and the atmosphere (possibly with the energy of the sun and lightning), hydrothermal vents are located deep in the ocean. They were discovered half a century ago, so that’s enough time to popularize the hypothesis about them as the source of primordial life, or at least its equivalent. Half as long is the known history of white hydrothermal vents, which may account for their lower popularity.

Conditions in the vicinity of the two types of chimneys are different enough to correspond to alternative hypotheses to each other. However, in popular perception, the differences may be blurred – ultimately, both rely on the fact that waters containing the substrates of life are coming out from under the ocean floor. Unlike the primordial soup, which was supposed to be full of organic matter eaten by the original heterotrophs, hydrothermal waters are the domain of autotrophs and, since there is no sunlight, chemoautotrophs.

How life originated on Earth – a summary of various theories according to Weiners

The authors provide details of both hypotheses and related theories, but ultimately reveal that they are most attracted to the latest concept, although still based on Darwin’s old intuition. In their view, it’s the so-called Darwin’s byline best connects the various threads and avoids problems that undermine older hypotheses. The fundamental difference between the two is that this time life would not arise in the ocean, but in inland waters. Either way – it was created in water. Or rather, in an aqueous solution. Clean water is not what life needs. Nitrogen, phosphorus, sulfur, carbon and many other dissolved elements are essential. And if life hits clean water, the products of metabolism will soon change it.

The book describes not only hypotheses about how life originated on Earth. Much space is devoted to modern molecular biology. On the one hand, there are new discoveries, such as further functions of RNA and substances once considered a mere building block of life or even a by-product. On the other hand, molecular engineering that allows the creation of artificial cells or protocells. All this, however, is still happening in the water from which life has emerged, but taking it with it.

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